Navigate to IdentoGO, the provider of FBI Fingerprint checks for Pennsylvania:

https://www.identogo.com/

Click on the "Get Fingerprinted" button at the upper-right of the page.

Select "Pennsylvania" from the drop-down menu and click the "Go" button.

Click on the large section with the heading "Digital Fingerprinting."  When the mouse pointer is within the "Digital Fingerprinting" area, "Select" appears at the bottom of the box.

Enter service code 1KG6ZJ and click the "Go" button.

Click on "Schedule or Manage Appointment" to start the process of getting a fingerprinting appointment.

Follow through the process of entering your personal information and setting up the appointment.

For most people, the closest IdentoGO location is the Minuteman Press on Old Route 30 near the Westmoreland Mall.