Log in to your Shakes and Fidget account and enter the game. On the right side of the screen, you'll find a "Mushrooms" button. Click on it.
Choose the pack of Mushrooms which corresponds to the amount from the reward you've selected on Gamehag and select paysafecard as the payment method.
After an other window appears, enter the code you've received from us. After reading the Terms of paysafecard, click on the "Pay" button.