Using Employee Filtering
Employee Filtering allows you to specify which instructors a series can be booked with. This can be helpful if you have a series that is only offered by certain instructors in your account.
To turn this on, open your series settings and change Use Employee Filtering to Yes. Click Save to update your settings.
After saving, open the series again and you'll find an Instructors or Employees tab at the top of the settings. Note that this may have a different name in your account. Click the tab to open it.
In the Available Instructors dropdown menu, select an applicable instructor, then click the Add button. This will assign the selected instructor to the series. Repeat this process for all associated instructors.