How to convert a standalone PHP - MySQL script to make it a Wordpress plugin


I have a PHP - MySQL script that has some functionality clearly divided among "admin" and "regular" users (just like Wordpress). Similarly, it has some screens used by admins and some screens used by regular users.

What is the quickest/easiest way to convert such a script into a wordpress plugin? So that, now the admin screens (of the original script) are shown to Wordpress admin, while the front end screens are shown to wordpress front end users?

What are the things I have to consider changing (in the original PHP script) to convert it to a wordpress plugin? Any of your expert guidance/advice would be appreciated.