Page Comparison

...

1. A customer with an existing Betfair account visits vendorapp.com and wants to sign up for the vendor application.  
2. The customer wants to purchase a 12 month subscription to vendorapp, so they purchase this from vendorapp.com.
3. vendorapp.com then call the Account API-NG operation getApplicationSubscriptionToken, passing in their Application Key, a valid session token (to prove that they own that app key) and the length of the subscription required.
4. Betfair return to the vendor a Subscription Token of the form ABCD-EFGH-IJKL.
5. The subscription is then activated by calling activateApplicationSubscription token, passing in the subscription token and a valid session token for the customer (in the X-Authentication header).

The activateApplicationSubscription service should be used in conjunction with the interactive login method

See sample code here  (e.g. https://identitysso.betfair.com/view/login?product=<AppKey)