Custom Post Types, Custom Archive Page, Oy

Greetings,

I’m seeking some insight and advice on a site I’m building, a shirt store. I’ve been successful in creating Custom Post Types and a custom archive page (doubling as the home page) to show each shirt (post).

(I should note that I’m more of a designer, and have little experience in PHP. More of a CSS guy, unfortunately in this case.) Despite several web tuts I’ve found and tried to implement, I can’t figure out how to:

– Add an image or thumbnail to the archive post display;
– Customize how the posts display on the archive page.

I know I need to work around the theme (I’m using Themify Basic though I don’t need to). I would truly appreciate some clear insight and advice on this. Thanks so much, in advance.