Can't seem to signup as affiliate to sell CoursePress?

Hello,

I'm interested in selling CoursePress as an affiliate. I Googled how to do it and came across this page:

https://premium.wpmudev.org/blog/wpmu-dev-affiliate-program-goes-public-non-members-can-now-earn-cash-from-referrals/

It tells me to create an account (I have one since I bought CP), then add my affiliate info on this page:

https://premium.wpmudev.org/wp-admin/users.php?page=affiliateearnings

However... when I go to that page it says:

"You do not have sufficient permissions to access this page"

How can I sign up to sell CoursePress as an affiliate?