buying an iPhone from the apple online store.

Hi all. I was toying with the idea of getting an iPhone from the online store. I selected the color and model just fine. Note ot anyone else purchasing, the three carrier buttons to select either AT&T, Sprint or Verizon, are not labeled. Anyway I didn't finish the transaction, but if I were to, is it easy to activate your phone and all of that stuff? Thanks for any help. Siobhan