Where's my jack supposed to be?

Look under the spare tire in the rear tire well.

Here is the step to follow (at your own ..legalese required) you do not even need to jack up the car. just parked the rear tire on a long 2x12.1. Remove the T relay from underneath the rear seat
2. Crank the car until it dies quickly to remove pressure from the fuel filter 3. I used a cardboard to slide underneath. once there, the fuel is located next to the fuel pump. Both a within their own plastic box right before the rear driver side tire. To remove the cover, i just unscrewed the 3 plastic bolts holding it and loosen two other screw for more wiggle room.4. Cut off the factory clamps. Start removing the 4 hoses connected to the original FF. Some gas will drip during this step. If you were smoking before, now would be a good time to stop.5. Connect new FF Don't forget to new clamps.
6. Replace FF relay 7. turn key to position 2 but do not start engine. While fuel pressure is building, go back to check for leaks.8. Put everything back together 9. Start car and you're done

Open the hatch back. On the left-hand side is a panel that you can open in which the jack resides. Take that out.

(If you want to use the spare tire, located under the trunk space...)
You will see a plastic disc on the floor of the trunk space (where you store your luggage/groceries/etc). With a flat head screw driver pop the flat disc up & off. This will reveal a nut that you can turn to lower/release the spare tire that is directly underneath it.

If your T&C is like mine, you have a plastic cover in the middle of each alloy wheel that covers the lug nuts. This plastic cover can be popped off with the flat/nubby end of the crow bar that comes with the jack. It fits perfectly into a slot on the plastic cover.

Once you get the plastic cover off, the 5 lug nuts are revealed to you. Before you jack up the van, even a little, I would try to loosen all 5 lug nuts, just a bit...to get them going. Once the van is jacked up, it will be difficult to begin to loosen the lug nuts.

With the nuts loosened, set up the jack so that once you begin to turn it, the slot in the jack fits right into the frame of the van. You will see the frame that fits the slot in the jack between the front tires and back tires, on either side of the van.

Once the tire you want to change is fully lifted off of the ground, loosen the rest of the lug nuts and remove the tire. Replace it and reverse the order of what you just did. Get the 5 lug nuts onto the new tire, but only snug them up by hand. Once the tire touches the ground as the jack is lowered, then you can fully tighten the lug nuts with the crowbar.

Hope that helps!

You didn't mention YEAR or MODEL, but if it is like most Lexus vehicles, the spare tire winch has a square "nipple" on the end of it, not a "slot". You slide the jacking extension square-end first into the tube and onto the nipple. (This usually requires connecting two or more jacking extension pieces together) You then use the lug wrench (which has a square hole in it) to turn the jacking extension to lower the tire.

While there is road side assistance that can help in times of need. It's imperative that every driver should know about how to replace a flat tyre. After ascertaining that the tyre is flat, you should check the link which will guide you to change the flat tyre with the spare one, have a look
=> DIY 10 easy steps to change flat tyre
=> How to Change Flat Tire

Heavy tools needed:
-Floor Jack
-Jack stands
-wheel chuck

Hand tools needed:
-3/8" drive ratchet
-12 mm deep socket (a 6" extension isn't shown but also recommended)
-1/2" drive breaker bar
-1/2" drive 10" extension
-1 1/16" deep socket
-1/2" drive 24 mm short socket
-oil catch can
-funnel

Steps:
1)Put the wheel chuck behind your back tire and Pull up your e-brake

2)Find floor jack position

3)Lift car until you can fit jackstands under the car
4)Lower the car a bit so that it sits flat on the jack stands and the floor jack still has a bit of pressure pushing up on the mount

5)Locate the reverse sensor in your engine and unplug the grey connector on it.

6)Right behind it is a 12 mm bolt you have to remove. Use the deep socket 12 mm, extension and ratchet to remove it and just move the metal braket aside a bit.

7)Now use the 1 1/16" deep socket to remove the reverse sensor.

8 )Now get under the car and locate the drain plug.

9)Use the 24 mm socket and the 1/2" drive breaker bar (if your socket is 1/2" drive) and loosen/remove this bolt. This WILL be messy so make sure you have your oil catch can under neath it.
Try to hold the bolt in place as the fluid comes out until a good bit has drained. This will prevent it from going everywhere. Just let it drain for about 5 minutes.

10)When it's done draining, replace the drain plug and tighten a good bit. It has an aluminum washer so it'll feel like it can keep tightening but just go until you feel it's very snug.

11)Lift your car off the jack stands and lower the car back down. Remove the oil catch can prior to doing this.

12)With car on the ground, grab your funnel and place it in the hole where the reverse sensor would go.

13)Add 2.5 quarts of your desired gear oil. You can use Redline MT90, Amsoil 75W/90 gear oil,...Just make sure it's GL4 compliant

14)Replace reverse sensor and tighten. Again, this also has an aluminum washer so just tighten it until it feels nice and snug. RECONNECT THE GREY PLUG!

15)Replace the 12 mm bolt and just hand tighten until snug.

16)Prior to starting the car, push the clutch in and move through the gears slowly. You should notice a nice, smooth gear transition.

17)Last, clean up, remove wheel chuck from rear tires, and go take it for a spin.

Enjoy!

Sometimes the rim will stick on the hub or brake drum. Get a big hammer (3-5 lb. hand sledge) and a piece of wood, a 2 x 4 about a foot long works good. Make sure the car is lifted and on a jack stand, dont just rely on the jack itself. Hold the wood over the inside of the rim this is so you dont hit the rim directly with the hammer and whack it good until the rim pops free. Make sure to hold the wood from the opposit end so you dont pinch or hit your hand. I just had to do this on my sisters focus last weekend. I hope this helps.

Jack should be either located under hood mounted to fender well or in a side compartment inside of the car behind the rear wheelwell or even under the carpet in the trunk where the spare tire sohuld be located. If it is not in those locations then chances are that someone has removed them from the vehicle