If you don't have one, you will also have to purchase a compatible grease gun and adapter to fit the CK injector tool. Don't know about you -- but "Zerks" is in a foreign language to me. I Did watch a Youtube on how it works. Couldn't be easier -- pull the cranks, insert injector, attach grease gun, pump fresh grease, out comes the old dirty grease, keep pumping until you see clean fresh grease. Have lots of shop towels on hand to clean off the old grease. Apparently you can get all the stuff you need at your friendly auto parts store.
Zerks is the common automotive grease fitting that has been around for more than 100 years.