New guy with a dumb question

[katpeeler]

I just got my first smart phone, a HTC Touch and Im just finding out that alot of yall have moved on and upgraded. Im not up to speed on the "abreviations" and slang going on in here. My question is simple, Ive looked around and I do want to put a theme on my phone. How do I do this??..I went to the thread but it lead me to a dead end. Do I need to unlock it??...I bought the phone from an individual so I do not have a contract with it thru my phone provider (Alltel)...Whats some simple things I can do with my new/old phone??...Thanx