Requirements - A Master Admin or a staff type with the following permissions:

•  Setup: can access setup
•  Setup: can access staff scheduled

Assign Provider To Scheduling

To access this screen click on the Setup > Scheduling > Staff Scheduled. Select trainer from the column labeled Employees Not Assigned and then click the Add button.

Edit Employee Scheduling Settings

Click on the trainers name to edit their scheduling preferences.

Setting Up Trainer Scheduling

Enabled For Bookings? - Click Yes button to enable employee to be booked. 
What Services and Classes Can Trainer Perform - Select the services and classes you wish the employee to provide. 
Normal Work Hours - Click and hold mouse button at the desired start time and continue to hold until you have dragged the cursor to the desired stop time.  Please keep in mind that the employee needs at least one 15 minute block defined to show up on the schedule.
Copy - You can use the copy utility to duplicate the time block you created in the previous step.

The employee is now activated for services and classes selected and will appear in the booking grid indication the services they are enabled to be scheduled for and will be available to add as instructors when adding a class.

NOTE:  Keep in mind that the employees are setup for the standard rate and pay for sessions and classes.  If the employee you are setting up is compensated differently you will need to go into the employees tab under each service they train and the instructors tab under each class they instruct and set their pay rate manually.