There is only ONE STEP to becoming a rep:
1. Register for the Back Office here https://ost.postaffiliatepro.com/affiliates/signup.php#SignupForm
You will receive a welcome email upon successfully signing up at this link. If you require any assistance please email firstname.lastname@example.org
It is FREE to join. You have one requirement to remain an active representative - you must purchase (or sell) at least one commissionable item (no minimum dollar amount) once every 6 months.
After you have been approved you can go to http://www.ooohshinythings.com/Back-Office-Walkthru_ep_69-1.html to learn how to set up your new back office.