Within Settings > My Business, click Manage next to the shop, followed by + Add Another [Barber/Therapist] (the button shows your own word for staff, e.g. Barber):

Firstly, enter their name as shown to clients:

Secondly, assign the staff member their services. You can select services from existing staff members and adjust these as needed:

You can also add new services specifically for this staff member using the + New button:

If adding a new service, remember to save with the green tick button.

All service attributes can be further edited later within Settings > My Business. If the list is correct, click Continue to finish assigning.

Then, set their default working hours. Click on a day if it needs changing and edit the availability:

You can then optionally tick Create [Barber/Therapist] login, as well as add their photo to display when clients book - both can be done later if needed:

Once you click Finish, they will appear within Settings > My Business where you can further configure their settings and services.