Hi there,
Thanks for opening up this subject 
My questions are easy but I’m not sure there’s an easy answer :
my thanks,
/ech
(The following is assuming that you’ve got your synth connected to your computer via MIDI.)
Click on the “Instr. Settings” tab, and you’ll see a section of the tab labelled “MIDI Properties”. Select the name of the MIDI port your Virus is connected to from the Device drop down, and click on the “On” button to the left of the “MIDI Properties” label. What this does is set up the currently selected instrument slot (i.e. the row you’ve highlighted in the top box in the top right hand corner, which by default will be the 00 row) as sending MIDI messages. Instruments can also host samples (up to sixteen each, contained in the lower box in the upper right hand corner) or VSTis.
From there, you should be able to hear notes on your Virus being triggered when you press keys on your computer keyboard, or when you press play after recording some note data for the instrument you’ve set up to send MIDI to your Virus.
You can also send MIDI cc data to it using the “*MIDICCDevice” device under the “Track DSPs” tab, under “Meta Devices” (see the manual for details on this. You can add automation for these CCs under the Automation tab).
Alternatively, you can manipulate CCs by using the pattern effect commands described in the Reference section of the manual under Pattern Effect Commands (either by using the generic effect parameter changers to change the sliders on a *MIDICCDevice, or by using the 90 in the panning row column way, which I haven’t tried out before).
You can also use the Virus as a MIDI controller to control Renoise (Configs -> MIDI -> In Device).
P.S. Can someone give an example of using the 90-in-the-panning-row, Send CC Change command?
90 4885
sends value 85 (hex) to CC# 48 (hex)
good tutorial btw 
can i hear an example of a virus controlling renoise and vice versa?
@Rounser : Thanks a lot!!! Your thorough help and tutorial have done the trick. I’m ashamed to see it’s that easy actually (I have my Virus just to experiment with sounds and now… Wowwie!!! I’m still trying to imagine the possibilities )
My genuine thanks for taking the time to help me out, it’s sincerely appreciated!
@Florian : will try but you may have seen that I’m a total MIDI-newbie. But I’ll do my best of course…
No worries. And thanks to It-Alien, I learnt something new too.