Trying to hook up a Visio 42 inch TV to my dishtv

Question

Hi I just purchased a Visio 42 inch plasma tv at sams club as a clearance item. I had the sales guy hook it up to make sure it works, but when I got home I cant get the tv to come on. I read the book but can tfigutre it out.

I have one cable coming from the dish network in the wall with three prongs red, white and yellow as well as I have 3 more coming from the dvr also red white and yellow. Not sure how to plug these in. Tried everything and the picture is just a bright green.

Need help