Download Strava and Garmin Connect app to your phone. Sync phone via Bluetooth to the Garmin. Create Garmin Connect account (you won't be using this much, at least I don't). Go on your ride. Don't use the Strava app to record the ride, just your Garmin. Stop your Garmin. Save your ride. Connect your phone via Bluetooth to the Garmin if it isn't already connected from your ride. Ride will automatically upload to your Strava.