As a Program Director, AMP provides you with complete control over the rosters of your teams.  Click the Roster button in the left navigation menu and then click the "Add New User" button:

This will open a pop-up window where you will be able to fill out the user's full name, email address, what team he or she is affiliated with in particular, and type of user he or she should be (Athlete, Coach, Program Director or Staff):

Different users have different roles in the site. Athletes can read content, Coaches can create and distribute content, and Program Directors can do just about whatever they want. If you initially set a user to be Coach, Program Director or Staff, you will not be able to change him or her to Athlete at a later date (without emailing for further assistance), but if you initialize a user as an Athlete, you can promote him or her to any of the other types later. Read How do I change a user's role? for more on this topic.

You will be able to edit the fields you just filled out after the user is created, so if you are unsure about any of them, make your best guess and you can fix the guess later. 

Once you hit , you will be redirected to a screen that tells you an email has been sent to the user. You do not have to wait for the user to respond to the email for the account to be active. The user is created as soon as you hit Register. You can start tagging the user in content, assigning workouts, etc. immediately.