To detect your Pixel XL 2 phone on Windows a driver must be installed.
these files will be contained within the zip:
To install the driver open Device Manager goto other right click the Pixel XL 2 with the warning icon.
Click Properties > Browse my computer for driver software
Select the directory the files were extracted to
Once installed the Windows Device Manager will detect the phone as an Android Device with an ADB Interface
When connecting your phone a message will appear: “Allow USB debugging?” press Allow on your phone.