1) copy all of your desired theme's code. (ask for the code)
2) go to your blog's customize page.
3) click "edit html".
4) select (command+a) all the coding there, and then delete it.
5) paste (command+v) your theme code there.
7) if you want to customize something, refresh the page and all of the customizable options will be there.
attention: you may edit the theme you want around, but please keep the credit
p.s: i make themes almost every weekend.
if you have any suggestions, please feel free to submit/ask me :)