In Rantevo a provider is a person a customer can book with. Bookings are made against a provider, not against the business, so you need at least one even if you work alone.
Go to Providers in the admin.
Adding someone
Give them a name, and optionally a photo and a short bio. Both appear on the public team page, and a real photo helps.
Then assign the services they offer. Someone with no services assigned will never be offered to a customer, and a service with no providers assigned can never be booked. Those two facts cause most "nothing is available" reports.
Their working hours
Each provider has their own hours, set on their profile. The times a customer is offered are the overlap of your business hours and that provider's hours. If the shop is open 09:00–18:00 and someone works 09:00–13:00, they can only be booked in the morning. Nothing you change on the shop's hours will alter that.
You can also add breaks, such as a recurring lunch. A break is taken out of that person's availability every week, so you do not have to split the day into two shifts.
One-off changes
For a single day rather than a weekly pattern, use Closures: a late start, a training afternoon, a day off. A closure can cover the whole business or just one provider. See Close for a holiday or time off.
Removing someone
If a provider leaves, remove them once their remaining bookings are dealt with. Rantevo will tell you what is still on their calendar rather than cancelling those appointments for you.