Identifying ADSB interference with Airspy



I think I have managed to set up ADS B s Spy ( which is receiving signals) and SDR sharp Airspy.  Well thats as far as I have got.  What I am trying to do is to check on local interference to my airspy ADS B receivers locally.  When I think I have dialled up 1090 mhz on the SDR, select Airspy in the SDR sharp, press the start, I get a no  device selectedc.  the airspy is connected to my PC and airspy is indicating signal being received.  Not seeing anything on the SDR sharp screens...... help