If you have purchased the Group Fitness Blue application through the in-app purchase, you can restore the purchase anytime you want.
The restore process is required is you delete and reinstall the application. Or if you install the Blue to another iPad that you own.
First, make sure you use the same iTunes account you used for the in-app purchase.
Then, follow the steps “Options -> Settings -> Subscription”.
In the top right corner of the screen press “Restore”