Install Guide Certificate via USB

This method applies to Mac users only

• Download the Apple Configurator 2 utility and open it
• Create a "New Profile"
• Choose "Certificates"; then "Configure"
• Browse to your trailers.cer file
• Save the profile
• Connect the ATV via USB
• An icon for the ATV will appear; right click it and choose "Add Profile"
• Browse to the profile saved in step 5
• Apply everything and disconnect from USB

What about Windows users ?

You may try the iPhone Configuration Utility