How to que a song in headphones DDJ-RB

When I'm playing a song in reckordbox on my DDJ-RB's I'm only ever able to hear song on the side that's currently being played and can't seem to figure out how to hear the next song that's being cued through my headphones, while keeping it so only the current song can be heard through the speakers. 

I seem to only ever be able to hear anything through headphones when I have the headphones master cue turned on, but turning on cue 1 or cue 2 makes no difference, then if I turn off the master cue while cue 1 or 2 are turned on I can't hear anything. 

These are my very first pair of decks so I'm pretty clueless so apologies if I'm just being stupid but hope you'll be able to help me out a bit.