Tuning Sat channels in through combi box

Hi, I'm in the process of trying to tune Satellite channels in ( through Sky dish - I'm a former subscriber) via combi box. All seems to be going well until I must choose an Antenna Instillation. At this point there is a list of satellites to choose from ( Eutelsat, Astra etc.), but I don't know which one to pick. plus a lot of the channels seem to be scrambled
Any Help very much appreciated.
Oh, and the combi box is Walker.