, here is how I do a fill system for my builds. http://www.fastfittings.com/plastic-push-in-fittings I use two T's and three shut off valves, you can usually find these at a hardware store. configured in this order T than shout off valve than the second T this should make a straight shot from one end to the other, now where the T's branch off is where the other two shout off valves go. now I usually would attach this right after the pump but any where will work. now you have the ability to force the system to flow throw a make shift reservoir. a 2 liter container or half gallon container works well for this purpose. attach hoses about two feet long to the ends of the two shout off valves, and put both of them into the container. you will need to fill the container with distilled water or whatever you use as a liquid coolant. ok so you know the direction of the flow, that is that, one of the hoses is putting water into the container. while the other one would be pulling water out of the container, pull the draw line out of the container. the easiest way I have found to prime a system is to either use a large syringe( not the type with a needle)but used for filling medical nutrition bags, for line feeders, or a squeeze bottle with a end that is large enough to be pushed into the end of the hose to make a tight fit. then start filling your system as much as possible by hand. then when you don't think that you can get any more air out of the system by hand. fill the intake hose as much as possible and shove it back into the container and turn your pump on. it may take a little time to get all of the air out of the system but the pump should be able to handle it from here. once all of the air is out of the system simply turn the intake and outlet valves off and the center valve to the on position remove the fill hoses from the shout off valves and you are done
this is just what i would do hope this points you in the right direction for your own build.