To use Screenly 2 Player with NEC's P and V series monitors, you first need to download the custom disk image. You can find this under the 'Add Screen' section within the web interface. You need to download the disk image called "Compute Module 3".
Once you have the disk image downloaded, you need to follow the instructions from the manual for the monitor on how to re-flash the Compute Module. In short, you need to change a setting in the menu and then use a software to write the disk image to the monitor. We recommend that you instead use Etcher rather than the software that NEC recommends in their documentation.
Once you have flashed out the monitor, you can power on the monitor as usual. Do make sure that you have the monitor connected to the internet over Ethernet prior to booting it up. Once booted, you should see a PIN code on the screen. Simply enter this PIN code into the web interface. With that done, you're set and you can start scheduling content to the screen.