You can upgrade your App.net account at any time to any of our account options. If you're currently on the free tier you will be asked to enter your credit card information to upgrade your account. If you're currently on the Monthly or Yearly Member tiers your most recent payment will be prorated and applied toward your new account.
To upgrade your App.net account log into Alpha and click on your username in the upper right corner:
Select Settings ->
'Upgrade Your Account' ->
Choose your desired subscription level. If you are upgrading from the free tier you will be asked to enter your credit card information for payment.
If you are currently on a paid plan but upgrading to a different tier you will be shown the prorated amount that your card will be charged when you upgrade and you will be asked to enter your password.