Adding and HD DVR receiver

I wanted to add A HD DVR receiver in a room, there are three other rooms in house that have receiver in them.

So my question is that this room only has comcast cable ran into it. Can I use that cable for my new receiver? What I noticed too is that when you look from the satellite there is one cable coming out to a 4 way splitter witch only has three lines running out of it going to the other rooms, so can i simply plug the old comcast cable into the splitter?