If you want to download an existing ride from your Ride History please view these instructions:
If you already have rides in your Ride History, you will need to upload them manually to Strava. Once connected, previous ride history will not automatically upload to Strava, only future activities will.
Menu → My Account → Linked Account drop down list → Strava
Once you select the Strava option from the drop down list, click on the CONNECT button that
The Strava site will open in a new window where you can finish the sync process.