You can purchase premium game time here. After purchasing your premium time, your premium tokens will be available ingame.
Each token grants one day of access to the premium areas of the world.
To apply the tokens to your account just right click on them in your inventory to add them. You can also trade tokens to other players, give them to your friends, or even sell them on the player market ingame!
Please note that the game is still in alpha and isn't finished, but your support during alpha testing is greatly appreciated!