Usually, Riverside automatically uploads each participant's audio/video track during the session.
If you left the Studio before your track finished uploading and you recorded using the Riverside app on a mobile device, open the app again to continue the track upload.
See the status of any remaining uploads by tapping the Settings (gear) icon and then tapping Upload Status. Leave the app open when finishing your upload.
If a track's upload percentage on the Upload Status screen does not increase, turn your mobile device off, then turn it back on and open the Riverside app again.