First, you'll want to select the Appointments option from the menu, once clicked you should see your entire calendar, like the one below.
From here, in the top right click on the "..." overflow menu and select "Manage diaries"
From here you'll select your diary, in the example below it is "Default diary".
You should see a screen similar to below if you have followed both guides mentioned at the top of this article.
To manage the services, click on the button under the "Services" header. Doing so will open a popover similar to the one below.
If your organisation only has a few services created, you should be able to see them all. If you can't see them all, you can scroll down to them in the popover.
Or if you know the specific service you are looking for you can use the search box to filter the list.
Selected services have a blue checkmark next to them, while unselected services have a greyed checkmark. When you click on a service it will toggle between selected and unselected.
Simply select the services you wish to be available on your diary and click the "Okay" button at the bottom of the popover.
Check that the rest of the diary settings are correct then click the "Save" button at the bottom and your diary will be updated to reflect the changed services.