Where do i inject the ink in my cartridges

Usually the refill kits come with instructions that cover many cartridges.

A lot of the lexmark's use HP style cartridges and those often you lift the label to access the fill holes.

FILL SLOWLY and do not over fill. Usually the cartriges hold so many ml and youcan measure that on your syringe. Knock off a few ml from what they say the cartridge takes.