If you have a Pro account, you have the option to make certain activities free for existing customers and members who have a specific subscription or other product. This is ideal if you sell a combination product with which you can, for example, follow a group lesson once a week and also have unlimited free training.
If you want to create an activity, for which people can register for free, follow the following steps:
Go to Activities
Click on New activity, and start entering the desired info
Click below Booking settings in the field "Credits per booking" on Free activity
Under Payment options choose "Free - only with linked products"
Then choose below Products with which product you can book this activity for free