In the Activities tab in the admin area there will be a blue ‘Add activity’ button, which you must select.
From there you must enter the type of activity (from a dropdown list) along with an activity photo.
Once you have saved your activity, you must then select the add session button in order to add sessions to this activity.
You will then be asked to select a start time, duration time, and a max capacity for the session.
Please Remember to save the session once you have done this.
If you wish to remove or cancel an activity, you can read this guide here