The short answer is that if you still have to ask this question you first need to better understand what real Satanism is.
Those who should join then usually want to.
We never try to talk anyone into joining.
If you are elite then you will know what to do and why.
In other words, the benefits of affiliation are found within affiliation.
Meeting with the few in this world like yourself can be reason enough for most.
Membership is considered a means of supporting the philosophy of the Church of Satan
so we think that it is important for anyone considering joining to have read and fully understood at least two of our major texts: The Satanic Bible by Anton Szandor LaVey and The Satanic Scriptures by Peter H. Gilmore. Both of these are available from bookstores in a number of languages.
Once you have digested both of these books, then the method for affiliation is made clear on the Affiliation page. Read it completely and carefully.