1 | Add the Service to Webcare. Find out how to do this here: Adding a New Service
2 | Add the Service to the Client you are wanting to setup appointments for. Find out how to do this here: Client Services
3 | Once these steps have been completed, you will be able to add an appointment in Client Scheduler.
If you need help on how to do this, you can find the article here: Adding an appointment to Client Schedule