I run phpMyAdmin v 2.51 on my local machine, and here is the deal... If this file is used to create the database itself, then all you have to do is type in the name of the DB on the home page where it reads: "Create Database" and click Create.
Once you do that, then select your DB from the left side, and in the right pane, you will see a tab at the top that reads: "SQL"
Select that tab, and either copy and past into the textarea at top, or browse to select the createdb.sql file in the box below, and click GO.
Your version may be different than mine, but the principals are similar enough, you should be able to find it now that you know what you are looking for.