Your Garmin account is properly synchronized with your Sport Is Life account. To upload the activities that you record with your Garmin device to Sport Is Life, all you have to do is synchronize the activity with Garmin Connect and a few seconds later the activity will be available in Sport Is Life. You will receive a notification indicating that the activity is available.
You can remove the connection between your Garmin and Sport Is Life accounts at any time from your Garmin account or from Sport Is Life, in the menu User Config. → External Apps.
Go ahead, you are ready to start training!