Remove the cordless drill from the charging station. Turn the drill off.
Remove the battery pack. The battery pack is located on the bottom of a cordless drill and can be loosened by pressing two tabs, one on each side of the drill. Once loosened, pull the battery pack downward to remove it.
Remove the battery cap. It usually just slides off, but it may be held in place with a small screw, depending on the cordless drill manufacture. If there is a screw, use a small Phillips-head screwdriver to unscrew the screw and then slide off.
Remove the old batteries. Place the new batteries into place.
Place the battery cap back over the batteries. If needed, screw the screw back into place.
Slide the battery pack back into place on the bottom of the cordless drill. You should hear a snap or pop when the battery pack is firmly in place. Allow the new batteries to charge for at least 24 hours before use.