To enable MyFitnessPal (MFP) integration in Boot Camp Challenge, you need to be logged into lolo connect (because the workouts upload there and then sync with MFP.) If you are logged in, under the Profile tab / App Settings, then you're ready for the next step. Go to the History tab and tap the 'lolo connect' button. Once that opens, there's a MyFitnessPal button on the top right. Tap that and it will take you to the MFP app to ask if you'd like to allow syncing. Once you accept, it will all just happen in the background for you as you complete workouts.
Note: you need to have the MFP app installed and logged in with your MFP account before starting the account sync steps above.