Your question is a good one but to dive in I have to go find what you downloaded then see if there is some theme manager noted. That's too much work so I'll ask you complete your post with the missing details.
I downloaded a few themes under the format .tsk. After i save them in my htc snap..i can't find the themes n can't apply them to my mobile. I would like to know if i am using the correct format for the themes and how to install & apply the themes for HTC SNAP.