Identify your BMW key fob type
Get the correct replacement battery
Press the release button and remove the metal key blade if your fob has one
Use a small flat tool or your fingernail to open the key fob case
Separate the two halves of the key fob carefully
Remove the old battery
Note the battery orientation
Insert the new battery in the same orientation
Reassemble the key fob
Reinsert the metal key blade if removed
Test the key fob buttons and remote functions