In order to activate bonus features from PayPal donations, do the following:

• Wait for the confirmation e-mail. You should receive it within a couple of minutes after you made the donation. (Check your spam folder!)
• In the app, navigate to Settings => Bonus features.
• Enter the e-mail you used to donate in ‘PayPal donation e-mail’.

The bonus features should now be activated. If they are not, feel free to contact me for help.