Turn on both units so they are in standby mode (should be a slow flashing blue for both.

Hold the jog dial button down on the Sena for ~8 seconds until it flashes blue really fast.

Hold the off switch on the Scala Rider G9 (middle top) for about 6 seconds, it turns off, but when you keep holding it it goes into the correct pairing mode (the same mode as pairing with a phone I believe) flashing purple and another colour, I think red...

Then on the Sena click the jog dial button once, wait a good 3-5 seconds, and they are paired!