If you are currently using a Yoyo-powered loyalty card, you can link it to the app when creating an app account. Once you have signed up, any loyalty you have collected will be visible on the app. Happy days!
If you already have an app account, you can also transfer the loyalty you have collected on your Yoyo-powered loyalty card to the app via the setting menu > Add a loyalty card. Please note that once your loyalty has been transfered your loyalty card will be deactivated.