Yes indeed, if you are using only one xbox controller, so edit you recalbox.conf
like this :
# ———— D – XBOX Controllers ———— #
## Xbox controllers are already supported, but xboxdrv can solve some compatibility issues
## Disable this if you use ps3 controllers
enable_xbox_drv=1
## set the amount of controllers to use with xboxdrv
xboxdrv_nb_controls=1
And to edit the file, as said before don't use the wordpad or notepad included in Windows. But download and use Notepad ++ or EditPad Lite 7. Once the xboxdrv driver activated, the led of your controller should be fixed on the player 1 position and stop to blinking.