if its anything like the 01-05 model, its a hole in the lower half of the back of the steering wheel, insert a screwdriver in there and push to unhook a spring clip that locks the airbag in position. once unhooked, the airbag will slip upwards slightly. then pull up from the top rear edge. it should unhook easily once unlocked.
always ensure you have disconnected the battery before disconnectig airbags etc..
make sure you have side lights on when reconnecting the battery in order to prevent power surges on the ecu/dashboard.