Dino Jeram

Hi All.. All very new to this. I brought a a5 recently and the garage only gave me one key as that what he had, according to the car there is three keys. I have already been in touch with my local audi dealer and will order up a new key Two Questions 1, how do electronically 'remove' the old keys 2, how do I program the new key or is that a Audi dealer thing only.. Look forward to your replies!