i would take it to a professional but this is what i did.
my airbag had already been deployed, my friend helped me with it so i might forget some part of it but, basically,
disconnect the battery(i don't know if it will deploy if disconnected but i would do this anyway)
there are 4 bolts/screw(not sure which,don't remember) on the back of the steering wheel that hold the airbag in, remove them.
pull out the airbag gently and hopefully it won't deploy, there will be a wire connector holding it on. use a screwdriver to pop the thing on the connector and then pull it off. you should now see the steering column with a nut/bolt(don't remember which),remove and then you should be able to wiggle the steering wheel off.
hope this helps but you might want to have a pro do it anyway...