Step 1: Go to Appointment Booking
Step 2: Click on "Edit Appointment Types"
Step 3: Click "Change hours" on Appointment Type of your preference.
Step 4: Change your available hours as per your availbility and the type of appointment you have.
If you have meeting type appointment type you will be able to select regular interval of time ranges by clicking on "Change hours". Learn more about it in this article.
If you have signup sheet type appointment type you will be able to select manually explicit hours when you wish to open your availability by clicking on "Change times". Learn more about it in this article.