The cartridge has a bolt in the bottom that you can remove without removing the housing. You pull that bolt off, then shove the top part of that plastic thing into the bolt's place, hard, and the oil is ejected from the filter housing through that spout of the bottom. The O ring goes around the bolt.
If you don't push it in straight enough and with enough force, the oil will go everywhere and your coworker will laugh at you.
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