wix booking: How do I connect staff to a service via velo?

Im creating staff using velo api:

https://snehatanushah.wixsite.com/bookingvelo/createstaff

Im able to create staff successfully, however not able to connect it to a Service. Is there a booking API , if I can automate this step?
I have already checked, but no luck : https://www.wix.com/velo/reference/wix-bookings-backend