In the Garmin Connect IQ app, open the settings for the app that sends data, and copy the User Id setting.
Open the settings for the app that receives data and paste the copied value into the User Id setting, and save the settings. (All apps that communicate to each other must have the same User Id)
After you purchase has been processed, all apps that use the User Id will be able to communicate with each other using the Dacrosse Web API service. No further action is required.