I am a satanist and want to pursue my singing for him. How do I start?

Regardless of whatever religious views I personally have, I think you should be able to pursue your goal. Just be aware that you will come across a lot of people who won't agree with what you are doing and will judge you. If you can live with that and are happy to continue then, that is your choice.

The other thing you need to do is to get your singing heard by more and more people of a similar persuasion. Social media is a god way of doing this, as you can upload and promote your singing for free, and you can also connect with likeminded individuals who share your satanic beliefs.

I found a website called Joy of Satan on which there is further information about Satanism and also various means of contact. I suggest that you contact the people involved with this who will probably be able to help you pursue your singing if only at meetings, etc. To begin with.

If you have a good singing voice, have you thought of using it for other purposes, such as singing pop songs in bars or colleges? You don't need to dedicate your life to religion in order to enjoy singing and to allow others to enjoy your voice too.