Hello There. In order to prime the cartridges you would have to remove a plug that sits at the top of the cartridges, close to where the tubing is attached to the cartridge. You must remove that clear round plug and that will expose a hole. Grab your syringe and stick the syringe(without the needle) into that hole to create an air tight seal. Once the air tight seal is created you are able to draw some air out from the cartridges. If you end up drawing a lot of ink, simply toss the ink back into the appropriate ink tank.
If you're not able to pull any of the air out then it will mean that the small plastic piece that connects the tubing onto the cartridges might have a clog, in that case should call our support line and we can send out replacement parts for you.