Had to do quite a few steep hills

First ride after a couple of weeks being away from home. Got scared by two cars. Need to find some quiet roads. Also realized something else. My Garmin watch often says it is synced to my tail lights. I never knew what it meant. Other than that I was frustrated the lights were not working after I had fully charged them. Then I realized… the lights come on moment I start my ride! I guess the Garmin watch is trying to save battery for me!! Now, I have no idea how to connect my front lights too!