The FP-10 piano has a 3.5mm (1/8 inch) headphones jack, while the headphones that come as part of the Roland FRP-1 Digital Piano Bundle (USA only) have a 6.35mm (1/4 inch) phono plug. At first glance it would appear that the plug on the end of the headphones does not fit into the headphones jack of the FP-10 piano.
The plug on the end of the headphones is actually an adapter that must be removed. Simply unscrew and pull off the headphones adapter. Underneath you will see the 3.5mm (1/8 inch) plug that fits into the FP-10’s headphones jack.
Plug the headphones into the PHONES jack on the rear panel.