In order to set up the VTO request, we'll need to first activate this for you. Once activated you can create a timeslot opportunity which will include a specific custom field unique to the VTO policy (it's called "Approval Request Person". This custom field will be used to store all the managers who will be selected for an employee to select upon submitting their approval to volunteer.
To start, create an event -> select timeslot and make it an open opportunity:
Once you create the timeslot shell you can customize this for all of the specific duration and hours you allowing your employees to volunteer or request time off for.
Then on the "registration settings" make sure to navigate to "Add Existing Saved Fields" and find the field called "Request Approval Person":
The following is the modal the end result (select it and apply):
Once this is done you can then save and publish this timeslot so that employees can then use it to request volunteer time off.