Photoshop to Theme – Help! :(

Hi everyone,

Please excuse my ignorance here ??

I am new to WordPress and certainly not a developer by any means but… if I have someone design a custom theme for me in Photoshop and I want to implement it, how do I know what code to use for the photoshop images? Is this a copy of a particular image (for example, a header image) into that particular section. I’m having some trouble finding out how photoshop (PSD files) are translated into actual working wordpress themes?

Thank you!! ??