Hire a developer or purchase a customizable theme. I don’t get the impression that the answer you are looking for can be easily and clearly stated in a brief manner.
You are going to need crash courses in Custom Post Types and The Loop, which are basically what makes wordpress what it is (which is why your question is much more loaded than you know).
If you want to include the ability to add custom types of data (i.e. audio, files, or custom field types [radio buttons, selection menus, dropdowns, extra text fields, etc]), you are going to have to learn about Custom Fields or check out this EXTREMELY helpful plugin, Advanced Custom Fields.
You will ultimately be editing the index.php file (or page.php, category.php, etc), to have them pull and display the exact data that you want to grab. For example, the standard wp-loop will grab 10 (i think) posts from the “Posts” post-type and display them on the page. If you understand how the loop works, then you can convert your site into a “dynamic site” in the sense that you mean. Making the backend customizable is an entirely different ballgame and will require a developer’s knowledge.
I hope that this helps!
j