The XGE Hexblade Warlock unlocks an ability called Accursed Specter at level 6.
Starting at 6th level, you can curse the soul of a person you slay, temporarily binding it to your service. When you slay a humanoid, you can cause its spirit to rise from its corpse as a specter, the statistics for which are in the Monster Manual.
My confusion here is that it doesn't mention anything about how this is done. I would assume that I just take it as literally as possible, that I need to be the one that deals the killing blow and it just automatically happens if I want it to?
It seems straightforward enough but wanted to make sure there wasn't something I was missing.