The toilet seat is super loose and I am unable to tighten.

Hope this will be helpful. How to Fix Loose Toilet Seat

Tighten the screws back up.

If you are trying to install a standard toilet seat on a special "smooth sides" toilet, it likely will not work. Most hidden bolt toilets come with a special seat because you cannot get to anything from below. This special seat has a set of expanding style bolts that are attached to the screw that is part of the seat. The plastic expanding bolt goes into the hole(s) on the toilet, and as you tighten the screw on the toilet seat bolts, they expand the plastic part in the hole of the ceramic toilet.

Is the nut thats on the under side fastened all the way and If you've done that and the screw keeps getting loose then the threads inside the nut or on the screw may be worn away. If thats the case, you may have to by some new screws and I'm not sure if they sell those separately you would usually have to buy a new toilet seat to get new screws, but try home depot or walmart.

When the seat is closed there should be two plastic extensions about one and half inches long, lying flush on the base. Open these with a small screwdriver, like a ****-shell. There should be a regular head screw there and correspondingly underneath the screw, a nylon nut. hold the nut and tighten the screw.

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If the screws don't tighten the either the screw threads are stripped or the attachment nut is stripped. Take the screw and nut to any hmoe repair center and get new ones. remember don't over-tighten then screws as this will crack the unit.

well there should be 2 hinges rite behind seat. you wont see the screws cause they are under a plastic cover. take a flat head screw driver and pry up cover. lil cover should lift up towards tank. then you should see screws. the nut is under bowl you have to bend down then look up to see them or do what i do and feel for them. take big flat head or big philips screw driver and while you hold nut titen screw. hope this helps. duane:)

Lift up plastic caps located on ends of hindge behind seat. use flat screw driver and hold the nut under the outside toilet rim with your fingers or a pair of pliers. Do not over tighten or might crack the bowl.

Reach under the bowl of the toilet and feel for a rather large wing-nut bolt on each side of the toilet. You must hold these with your hand and tighten the screws with a screwdriver. If you don't hold these wingnuts, then the screws will keep spinning forever and never tighten. Run your hand directly below the toilet just below the screws and you will find them. VERY EASY FIX!

Use a flat head screwdriver to pry open the plastic pieces that cover the screws. Using the same flat head screw driver, unscrew the large plastic screws holding the old seat in place. There are usually plastic nuts on the underside that you can hold on to while removing the screws. Remove the old seat. Clean the area where the screws were and dry thoroughly. If the new seat has an adhesive pad, remove the covering from the adhesive and put the seat in place. Thread the new screws through the holes and attach with the new nuts. If there aren't new nuts and screws, you can use the old ones, provided they weren't damaged during removal. Snap the caps covering the screws on the new seat in place. Be careful not to over tighten the screws! Since they're plastic, they can be easily damaged by a screwdriver!