At the moment there is no automatic way available to connect your Bike Citizens account with the Bike Data Project. We strongly hope that Bike Citizens will soon provide an API which allows cyclists to export their data.
Meanwhile, you can do the following to share your Bike Citizens data with the Bike Data Project:
Open the Bike Citizens app and go to Dashboard and then My tracks.
In the track list you should first swipe a track to the left (iPhone) or long press a track (Android) and then export them via the share-symbol.
Go to https://www.bikedataproject.org/ and upload your tracks.