I think maybe you are confused. From their FAQ
DO YOU WORSHIP SATAN? No, nor do we believe in the existence of Satan or the supernatural. The Satanic Temple believes that religion can, and should, be divorced from superstition. As such, we do not promote a belief in a personal Satan. To embrace the name Satan is to embrace rational inquiry removed from supernaturalism and archaic tradition-based superstitions. Satanists should actively work to hone critical thinking and exercise reasonable agnosticism in all things. Our beliefs must be malleable to the best current scientific understandings of the material world — never the reverse.
There is a church of Satan, how they compare is here
An asshole mostly, but that's another issue. Helps you think through problems because you think about it before doing it. When I read fiction I try to imagine other voices. I read a lot when I was younger.