First remove the key completely from the ignition. If it is inserted it can set an airbag code.

Remove the upper cover, disconnecte the battery cables, and pull up the fuse box. The fuse box can be held out of the way using a bungee cord.
Then remove the 5mm hex bolt securing the power steering reservoir (if present).
Then loosen the 10mm bolt at the bottom of the battery box.
Now it should be possible to unclip and remove the corner of the box nearest the engine. Using a 13mm socket remove the battery clamp at the bottom front of the battery. Finally to remove the battery it must be tilted nearly on its end to remove otherwise it wont fit out of the opening. It is fine to tilt the battery as long as you move quickly to minimize any possible leakage.
Installation is the reverse of removal.

Once connected turn on the car and then turn on the radio to make sure it is out of safe mode. If it is not, turn off the radio, then turn off the car, then turn on the car and then turn on the radio. Usually this procedure will fix the safe mode issue. If not look in your owners manual for the radio code and enter it.
Set the clock and your done.