just purchased theme template - where do I go to design it?

I may be super inexperienced but I have worked with templates before and usually have no problem customizing them with my own images, text, etc.
I can't even find where to go to be able to do that??? can anyone tell me what to do once I purchase and download the template? I've opened the downloads but I am not in IT so they mean nothing to me? does this template have a design studio or edit studio???
sorry to be so lost!
Daisy