Loop the cable around the chinguard on your helmet (or D-ring) and back through itself into a choker, pop your seat and put the loop end around the little hook under the rear seat of your R or if you have an S... the shoulder bolt that the seat hooks guide on. Replace the seat and your helmet can still be stolen by a 8 yo with tweezers. LOL.
I don't like popping the seat all the time, especially when I have the bags on Stella, so I came up with this because I have an aversion to extra keys:
https://www.masterlock.com/personal-use/product/1548DCM
I bolted a short section of thick cable through this MasterLock carabiner thing and hung it down by the shock. It's out of sight and I can get 2 helmets locked through the D-ring! (barely).