The Church had an influence on Satanism, but since Satanism is an individualist philosophy, they do not have the final word on what all satanists should believe. Satanists generally have varying beliefs about what is Satanic and what Satanism means on a personal level. Because of this, there are a variety of beliefs and mythologies that have influenced the practice of Satanism. Since there are different views and methods, it seems to me that there is no final definition of Satanism beyond what the Satanist creates for their own practices and beliefs.
Since there are many methods of expressing Satanism, you have to find the one that suits you the best. Only you can know what is right for you in the end. Your choice should be a spiritual or philosophical commitment that is based on an informed decision. In my opinion, there is no one right way to be a Satanist; they are all forms of Satanic expression. But, no matter what the origin of our beliefs, as Satanists, we are all a part of the current of Satanism.