Keep in mind, an occult member comes to Christ the way anybody else does. He has to recognize he is a sinner, Christ died for him and rose again, and place his trust in Christ alone to save him.
At the same time, let me offer some guidance. First, your most powerful resource is prayer. An occult member has the same problem every non-Christian has, he is spiritually blinded: “But even if our gospel is veiled, it is veiled to those who are perishing, whose minds the god of this age has blinded, who do not believe, lest the light of the gospel of the glory of Christ, who is the image of God, should shine on them” (2 Cor. 4:3–4).
Only the Holy Spirit can dispel the blindness and cause them to see their need for Christ. Through the Holy Spirit, God can get through to anyone, including Satan worshippers.
Second, let the truth of Scripture be your authority, not your emotions. Some may get angry over your words, but don’t respond in kind. Otherwise, Satan himself wins. Few things are more convicting than if they get angry with you, and you remain calm and collected.
A final thing is to challenge them to disprove the resurrection. They can only throw Christ away if they disprove the empty tomb, because that is the truth on which Christianity stands or falls. Challenge them to study the evidence behind the empty tomb and determine if Christ was the one He said He was. If they are willing to study the proof behind the resurrection honestly and objectively, God can use that to bring them to Christ.
Whatever you do, recognize that God can get through to anyone, even an occult member who seems far from God. Practice patience and let God use your witness one step at a time to lead them to Christ.