It was satire. He was trying to be clever. A bit too clever though, because some of his followers lost sight of the joke and started believing in the thing as if it were real.
In the clip from the History Chanel below, one of Lavey's followers puts a curse on somebody. His words are bitter, painful, and yet, hauntingly beautiful -- and for me pretty familiar.
Below is a clip from the 1964 film The Seven Faces of Dr Lao, where Tony Randall as Apollonius tells the sad future of a shallow woman. LaVey didn't start his church until 1966 so clearly those pesky satanists stole their cursing ceremony from the George Pal Film. I bet none of them even have a clue.
In case you're worried the film is all like the dark scene above, consider this one a little later, again with Tony Randall, this time playing Dr Lao explaining how there is magic in everyone's life.