Try and post some pictures of your plumbing system.

First make sure your strainer basket housing winterizing plug is not leaking air and that your strainer lid gasket is good. Put the multiport valve in the recirculate position then close the skimmer and the main drain valves. Remove the pump strainer lid and fill to the top with water. Put the lid back on then start the pump and open one of the skimmer valves just a little until the water stops comming from the inlet pipe then shut the valve and turn the pump off. Then open the pump strainer lid and fill with water again. Keep this cycle up until you get a good flow thru the one skimmer. Once you establish a good flow thru this one skimmer then slowly open the other skimmer (or main drain) until the pump starts to unprime then quickly shut the skimmer (main drain) but keep open the one skimmer with good flow. After you establish good flow again then open the other skimmer valve (main drain) again unit it starts to unprime then shut this valve again. Keep doing this until you have good flow thru all your skimmer and main drain valves. Every time you shut the pump off make sure you close all your inlet valves. You also may want to put a check valve on the discharge side of your pump. Hope this helps.