To install or update Screenly on your Raspberry Pi 3/B/B+ or Box 0 player you will need: an SD card, an SD card reader, and the free program Etcher installed on your computer - you can download Etcher here: https://www.balena.io/etcher/
If you do not have an SD card reader you can buy one here:
This video has a quick overview of the steps involved:
1. Download and Install Etcher
2. Log in to Screenly.io, go to "Screens" and click the "Add Screen" button. On that page under "step one" click the button to "Download the Screenly disk image", this will download a .ZIP file with the ISO inside. (An ISO file is a Disk Image, you will use Etcher to write or 'flash' your SD card with this disk image in the next steps).
3. Plug your SD card into the SD card reader and the reader into the computer if it isn't already. In Windows you might see a pop-up asking you if you want to format the SD card, click cancel or no.
4. On your computer open Etcher
5. In Etcher there are three steps:
a. Click Select Image - find the .ZIP or .ISO file that you downloaded in step 2, select it and continue. If you cannot find the file you downloaded: go back onto your web browser, then on your keyboard hold CTRL + J. This will open a new tab with your download history. Find the screenly file in the list and click "Show in folder" to see where it is.
b. Click Select Drive - Your SD card will show up as a disk drive on Windows, find and select it and continue. Your SD card will probably be drive D, E, F, or G. The Icon next to it should indicate that it's a USB or SD card.
c. Click Flash! It will take a minute or so for Screenly to be flashed onto the SD card
6. Once Etcher is done flashing the card you want to go to windows explorer, right click on the SD card drive and select "eject", the drive will then be safe to remove.
7. Remove your SD card and plug it into the tiny slot on the bottom side of your Raspberry Pi motherboard.
7. You're done! Put your player back together, plug it in and continue with the setup.
If you get stuck somewhere let us know at firstname.lastname@example.org and we'll do our best to help.