How do you add transmission fluid

Hello, The drain plug is actually the drain/fill plug. You heat the transmission to 35C by running the engine, then remove the drain/fill plug, connect your pump, and leave the transmission in park while you pump fluid into it. When you have enough, release the fluid back into the pump, or remove the pump and pour the fluid into a drain pan. When it stops overflowing, it is full. If you knocked the overflow tube off, you have to remove the transmission pan.