Petar 5, the access should be immediate if you clicked through the "click here to proceed to order form" button directly (if it's Clickbank). If you paid through Paypal directly using the Rocket Languages email address, then it's a manual process and you may need to email support.
Also, did you create an account already (for the trial version) when you purchased through Clickbank? And if so, did you use the same email address that you used for the payment? If it's the same email address, it should be seamless. If it's not, you probably need to log out of the trial account and log back in using the email you used to order, then you should have access to the premium tab.