so using vp-1020a you can only watch one sat at one time, even you got mulit-sat dish . Unless you replace that switcher with DiSEqC 1.2 switcher ($15-30).
VP1020a has LNB in and Out. so you can either connect the lnb cable from dish (most dish LNB has four LNB out) to LNB-in connector, or move the cable form reciver lnb-in to vp1020a lnb-in , and vp1020a lnb-out to reciver lnb-in.