Unless your talking about an auto? In that case, you drain the fluid by removing the pan (if there is no drain plug) and fill it up through the dipstick tube.
as 88SC_GT said.. both the fill plug and the drain plug are on the passenger side of the transmission. The plugs accept a 3/8" ratchet with no socket. A 3" extension on a 3/8" ratchet works perfect.
You'll need a pump of some sort to fill the transmission, or you could a) remove the shifter and slowly fill the transmission through the top, or b) remove the shifter boots and use a long funnel routed through the hole in your floor, and into the fill hole and fill it that way.
Just to hammer it home, the fill and drain plugs are disguised - they look like plugs with a square in the middle (if you are lookin for a bolt, like on your oil pan, you can look for quite some time).
Do be sure you can remove the fill plug before you remove the drain plug. I once had to fill a car (with a drain which faced the floor) through the drain plug. I had crazy rubber bushings rigged up - and it took gear oil. Arrgghh.