To manually add a BJJ session to your Apple Watch, open the Health app on your iPhone > Browse tab > search for "Workouts" > tap on Workouts > tap "Add Data" > select "Martial Arts" or "Wrestling" as the Activity Type > tap "Add" to finish. The best kind of data to add to your Health tracking app is by using fitness tracking devices like the Polar H10, or WHOOP 4.0, as these devices will collect much more accurate data together and automatically sync to Apple Health.