I just built my FT-6 and it came with the SKR board. Check out the documentation on the Folger Google drive. You will need to download Visual Studio Code and grab the Marlin firmware from the gdrive (I never checked if my printer came pre-installed on the SD card).
I don't know much about adjusting firmware but you will need to change the X-Y dim size in the firmware to match your printer dim.
I also googled the board and found a picture (I think from the manufacturer) that had nice labels for where everything should go,