Because of the seriousness of occult activity and particularly the use of occult symbols for these tattoos, I referred this question to our spiritual advisor, Father Edmund Sylvia C.S.C.
The optimal solution to this problem would be complete removal of the tattoos. But if that can't be done, you must do your best to cover them as much as possible because these symbols could be a source of scandal to others.
Assuming that you have performed the necessary confession and formal renunciation of your involvements in the occult, Father recommends that you also seek deliverance prayers and the formal renunciation and breaking of all covenants. This is very important "to prevent harassment and serious spiritual attack," he says. "As part of deliverance prayers, there should also be a 'sealing' of these tattoos, much like the formal closing of 'portals'" (which are doorways to the occult/spirits).
Priests affiliated with the Catholic Charismatic Renewal are usually trained in these areas. Check to see if a Charismatic prayer group meets at a parish near you and contact a member of the group. They will be happy to help you find a priest.