The A1502 uses the same keyboard from late 2013-2015.
Take out the board, heat and remove the battery (long painting knife and isopropyl recommended, don't puncture the battery), remove the backlight sheets and pull the keyboard out. Pull the rivets out using wire cutters and replace with screws over the new keyboard (search "a1369 keyboard screws" on eBay), then reassemble. Before doing all this, make sure to test the keyboard beforehand, by plugging it in.
Follow this video for the process (for the older A1425 model, but it is the same process, just different board and battery layout) https://www.youtube.com/watch?v=oq0nEyDhWTA