RideOns, those digital and social power vitamins we receive while we're riding on Zwift, are a great way to recognize a rider for a hard effort, or just to say "Hey, ride on!".
But you may get RideOns in-game that and miss the opportunity to see who gave you the RideOn to reciprocate them back.
You can look on the Zwift website after logging in, to see who gave you RideOns during your ride, but that's after the ride has been saved nad uploaded to Zwift, not during the ride.
From there, you can go back and find those riders in-game and give them RideOns via the Zwift application itself, or via the Zwift Mobile Link (ZML) app on your handheld or mobile device.
Finding other riders on the course and giving them a RideOn is the same process on the mobile device. See "How do I follow/unfollow others using the Zwift Mobile Link app?" for more details on how to do that.
Good luck and #RideOn!