the same place you check the fluid from, get a funnel with a small end on it, remove the dip stick, put the funnel in the same hole and add. Be sure to check the level and do not overfill it, autos are very particular about how how much fluid is in them.Be sure it's not the engine oil dip stick!! Also, the dip stick should say on it when to check the level of the fluid... most cars you check the tranny fluid when it's idling in park, but some honda's automatics are checked with the car off.