Heres picture of a spliter http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=picture+of+a+tv+spliter
if your talking about the main vermin cable coming into your house,use a splitter as stated above,but you will lose a percentage of your signal strength..more if your not on a minimum sub.. if your talking about using one box with two tv's,then thats a different ball game...