E70 Keyfob Reprogramming

One of my keys does not work when I press the lock, unlock or rear hatch button. However, the convenience feature of locking, unlocking when grabbing the handle and when putting in the ignition still work. The key fob was accidentally submerged in water. I have dried it out totally and I have changed the battery. When I 1st changed the battery it worked for a few key presses. Does anyone know how to reprogram the key fob? Every link on the website that I can find is for the other key styles where the key inserted in the ignition and turned. This has a 'start/stop' button with a key fob slot in the dashboard.