Note the following is adapted (from the vendor docs) for my Artik 520 board, with the following markings "Ver. 0.5 2016.02.05". It arrived with Fedora 22 installed. The following are notes from upgrading the board to Fedora 24, using the image provided by the vendor.
1) Get the firmware image from: https://developer.artik.io/downloads (hint: search for "artik 520 firmware"). Download the most recent version and burn it to a SC card. On Linux, I used "dd if=/home/tim/newfirmware.img of=/dev/sdb bs=1M" (without the quotes). Note: this is only what I'd used. On your rig it will most definitely be different. If you've not previously burned images to SD cards with Linux, DO NOT JUST COPY AND PASTE THE ABOVE. Once the image is installed, eject the card and insert it into the SD card reader on the Artik board.
2) Before turning on the board, remove the power and the serial connections. Find SW2 and move both switches to on. On a new board they will be in the OFF position. When both are OFF, the board will boot normally. When both are ON, the board will boot from the SD card.
Note: The web site shows a Ver. 0.5 board, manufactured 2015.12.23. My board is a Ver. 0.5 board, manufactured 2016.02.05. Although connectors are in the same location, much of the components (including SW2) have been moved. On my board, SW2 is just to the left of the antenna which is next to the SD card holder. It is recognizable because it is the only component with a glob of amber-colored plastic on top of it. (Looks like the photo on the web site, only in a slightly different location.)
3) With the power switch (i.e., the rocker switch) in the off position, connect the serial and power cables to the board. The two LEDs next to the serial connection will light up.
4) Start the terminal monitor (I use "sudo screen /dev/ttyUSB0 115200").
5) Turn the rocker switch on and press SW3 until the terminal monitor shows activity. Various things will load and you will see a progress indicator, just after the message "Please wait until the fusing has been finished."
After you see "Fusing is done. Please turn off the board and convert to eMMC boot mode", the board should return to the command prompt. Ignore the "sh: can't access tty: job control turned off" message.
6) Turn the rocker switch off and remove the serial and power cables.
7) Remove the SD card.
8) Return both SW2 switches to their original positions (i.e., OFF).
9) Reconnect the serial and power cables.
10) Start the terminal monitor (Again, I use "sudo screen /dev/ttyUSB0 115200")
11) Turn on the rocker switch and momentarily press SW3. You should see a normal boot sequence in the terminal monitor.
Once you see the login prompt, you're done.
Note: the root password will have been set back to "root".