This content is for an older version of Synfire. The current version is more streamlined and advanced, but most of the functionality shown here still exist.
Learn how to synchronize Synfire with Cubase 8 using Drones and how to export your composed music to Cubase with drag & drop (note that the music example is totally random - Synfire fits any style).
Go to the main menu and call Studio >> ReWire >> Transport. The small window opens as shown in the image below. Turn on the ReWire audio channels of Transport. That will enable Transport for the Cubase project. You might need to do a Playback >> Reset in Synfire (or restart Synfire) for the change to take effect.