Well, for starters you should make sure you install audio realism bassline to your Cubase VST folder. It will usually install in there by default but just make sure.
Boot up cubase and then open the VST instruments window (In devices)
Select Audio Realism Bassline in one of the slots.
On one of the Midi channels on the sequencer select Audio Realism Bassline on the midi out section.
You should then be able to use ARBassline, either by using a midi controller to play notes etc. Or draw in a section on the sequencer (with the pen/pencil) tool then double click on it to open up the Piano Roll and draw notes in.
Pull up the vsti either from the VST Instruments window or by clicking the little synth icon on the channel/track and then play with the settings to your hearts content. I can’t really tell you much about how to use ARbassline as I’ve only used it briefly. I prefer D16’s Phoscyon.
I hope that helps. It’s all off the top of my head because I’m not on the machine with Cubase on to look at step by step.
