Okay, here's what I don't understand. Say I ask a Disigner to help me with a design. Then what happens? How do I get it to download to my computer in order to print it?

My DH is all hot to get some for our cruise and I found some neat designs in someone's photobucket album. Now what? Jeez, what a can of worms I opened!
I tried to figure the steps out but I couldn't find that info on any of the stickys or threads. I know lots of you have done shirts, so as usual, I come to you for help!
TIA!!