I want to wire a 250volt 15 amp ac receptical

This one's an easy one. If you're comfortable doing this yourself, great, if not, I'd strongly recommend getting some help with it, though. No need to get injured or killed over this. If you and your friends aren't comfortable working with electricity, be safe and call an electrician. It'll only take him or her about 30 minutes and $70 in materials to do this for you.

First, locate and turn off the breaker feeding that 240V outlet. Put a piece of black tape over it and tell the whole family to make sure noone turns it back on. Take the cover off of the existing outlet and use a voltmeter to verify that it's dead. Now, take the screws out of the outlet so you can pull it out from the wall and disconnect the wires from it. There should be a black wire, a white wire and a bare wire. If not, let me know. Now go to your local Lowes, Home Depot, or other DIY store and pick up a NEMA 5-20R GFCI outlet. It'll look like all of the other outlets in your house, but it will have "extra" sideways slots in the middle of the tall neutral slot. This outlet is designed to handle higher amperage loads and some larger air conditioners will require it. Connect the black wire to the gold-colored screw on one side and the white wire to the silver colored screw on the other side. Connect the green or bare copper ground to the green or silver screw on the top. Put a couple wraps of black tape around the outlet and put it in the wall with the cover.

Now, back to that 2-pole breaker...you'll need to replace it with an inexpensive 15A breaker (to fill an empty slot and prevent someone from putting fingers where they don't belong) and a 20A AFCI breaker. Yeah, they're expensive as heck, but assuming this is in a living space, they're required by code and will help protect your family againsta fire. Make sure to install it as per the instructions it will come with. Assuming this is wired to Romex wire, you'll need to connect the white wire to the neutral bus (the bar full of screws where most of the other white wires are connected) and connect the black wire to the new 20A AFCI breaker.

Now, if you've wired it all correctly, you'll flip the breaker and it won't trip. (If it does, go through your connections and make sure nothing is shorted out. If you still have a problem, play it safe and call an electrician.) Go to the outlet hit the test and reset buttons a few times to make sure if functions correctly and you're good to go.

Hope that helps.