activate input 3 at UR-RT2?

It’s been more than a year since I did it, but I cannot seem to remember how to record sound from inputs 3&4.
I have connected the line out of a deck (cassette player) to the line input 3&4 in the back of my UR-RT2. I am hearing sound in Cubase but I cannot record it. In the Studio Setup at Cubase I see that inputs 3&4 are Inactive. Can you remind me how to activate them? I also remember that last time I used that to record from the deck, I did not hear the sound from it (unless I checked the monitor, I think) so I could still be doing other things at the same time, using UR-RT2 as the sound driver, e.g. watch a film.
Thank you!

Connect the Hardware Port to the Cubase bus in VST connections

Thank you!
How can I not hear what is being recorded? I.e. use UR-RT2 at the same time as an input/output source from my PC, for example to watch a film. I remember I was able to do this. Turning the monitor off does not seem to have any effect.

I remeber this was somehow automatically done by the UR-RT2 and the Cubase - I don’t recall configuring something to this end. The effect was that: Input being fed through Line inputs 3&4, recorded at cubase, while I do NOT listened to what was being recorded, and I could, at the same time that the recording took place, listen to something else, like a video, its sound being played back through the UR-RT2. I cannot seem to recreate this “multitasking” effect…

Found it!
In the UR-RT2 standalone application I turned the “daw” bar volume to zero!