Using a prying tool, or fingernails if you prefer, carefully lift up the locking bar, releasing the ribbon cable from it's connector on the logic board.
The ribbon is quite delicate, so if you encounter resistance while disconnecting it, stop and make sure the connector is unlocked. Don't pull sideways or diagonally as you may tear the ribbon.
Now locate the one and only screw in this keyboard. Treating it with the utmost respect, carefully unscrew it and set it aside - savouring the moment - because later on you'll wish there were more of them.