there should be a bolt on the side of the box, undo it and the fluid should be level with the bottom of the hole or just a smidge below (feel with your finger).
if its low use a pump/syringe to put more in.
but if its auto, there will be a dipstick in the engine bay to check the level.
Or just pour it throught the shifter hole (manual)
As for what type of oils, when you go to buy some, there will be a booklet there, look for your car in there