Inserting in multiple tables and joining data

I am using DW8, PHP and MySQL.

I've created a database for software inventory. One table is a list of software products and the other is the licensing information. I set it up this way because we have a product such as Windows XP that will have different licenses. But the end result will be someone clicking on Windows XP and seeing all licenses for that product.

I've created a page to insert into the software table and one for the licensing information. Now I need to make a third page so that the user can select the product from a dropdown menu and then enter the licensing information. I have join setup between the tables in the MySQL backend. How do I tell Dreamweaver that the license being entered is related to the correct product?

Thanks!