Here it is in a nutshell.
First you'd need to save your PSD template as web images and HTML.
Rename the HTML files to PHP files.
Match the PHP files to the names of WordPress template files (header, footer, index, etc).
Insert the WordPress specific PHP code into those files.
Since you don't know WordPress, best start at http://codex.wordpress.org/Theme_Development
As for SEO, most free and many premium templates I've seen have optimization issues, most common is misuse of header tags on each page.
The Home or Front Page should have the site title & description as H1 and H2 tags. Posts listed on the Home or Front Page should use the H3 tag and sidebar titles should use the H4 tag (WordPress uses H2 by default so you have to specify this in
Posts and Pages should have the post/page title as the h1 tag, not the site title.
There's quite a bit into writing a proper WordPress theme that is SEO optimized, so doing it your first time by yourself is going to take awhile... :( Maybe I should do a tutorial.