- Start creating HTML Forms and learning PHP's $_GET and $_POST variables.
- Read the mysql and its functions documentation online from php.net
- Read about SQL Queries and the ways to execute especially SELECT Query.
- Also, Try to learn a little of javascript as well. As a little part of it might be required for onclick events.
Edited--
AS per the comments above, like you said, it was for wordpress. I'd say you refer to the Wordpress Documentation as well especially the get_posts() and get_post() functions. You can also lookup for wp_get_attachment_image() for showing just the post images :)
Thats it. Glad to help :D