Actually, you hold the unlock button, and press the LOCK button 3 times. Your door locks should then lock and unlock. Then go right to the next key, hold unlock, and press lock 3 times, and the locks should lock again, and unlock.
On the 5 though, you could have a fuse blown for the locks. Look in the right rear, behind the panel, above the battery. There is a fuse there for the fuel fill door, and it also powers the locks. If it's blown, you'll need to replace the lock actuator for the fuel fill door. It blows the fuse.....have seen it many times.
The actuator is in that same area. You could simply unplug it if you want to.
Replace the fuse, and do the initialization procedure mentioned before.
I've posted a FAQ on that procedure........