To take advantage of Private Tours service type you will have to set at least one Car through Car management "Use for Private tours?: Yes". 
Private tours service type will automatically appear in the Service type drop down at the front-end if you have at least one car set to use for private tours and at least one Private tour created.

After you Save the car, go to the Private tours section.
Click on "New" button in the top left corner of the page.
Name of the tour: - this is the name of the tour as it will appear at the booking form drop-down selection of tours after a user selects Service type > Private tours. Example: Windsor castle
Published: Yes/No - before your Private tour goes live you can keep Published: No so it is not shown at the front end.
Number of hours: - indicates how long it takes to complete the Private tour. 
Next, select the POI for Pick up.
You will see a list of all cars set up "Use for Private tours?: Yes" with a brief information on the number of passengers and suitcases they can accommodate. 
There is a "Price" field at the end of each Car section. Here you specify the Price of the Private tour for this car. 

Note: Private tour pricing is for the whole vehicle, not price per passenger.

Description: - you can use this rich text area to write a description about your Private tour. Description will be displayed instead of the Google Map at the front end booking form.