Rack synth output into CuBase 8 audio file

Am using a Steinberg audio interface (UR44) with Cubase 8.0.5. Mike inputs give good results, but I want to plug a rack synth into line inputs 5 and 6, and record an audio file in Cubase. Established a midi track and then tried to get that sound into an audio track with no success. Could be a problem with VST Connections in Cubase, but establishing such a connection is beyond my experience.