My 1999 Renault Megane 1.6 Automatic Scenic is getting jerky.?

When warm the car seems to stick inbetween gears the revs climb and then suddenly it changes jerking the car violently. After reading some online info suggestions seem to lean towards lack of transmission fluid. I had a look at the weekend but couldn't find a filling point or dipstick. Can someone tell how to check the level and top up if required. Any istsance appreciated. Cheers Steve.