What are the steps for the tenant to evict an occupant, whether they pay rent or not?

Depends on the terms of the occupancy. If this is someone you invited to live with you and is not on the lease, then you are their landlord. The rules apply as they would any landlord/tenant relationship.

Without knowing where you are, we can't tell what rules apply. Generally you serve them a written notice to vacate within 30 days. If they don't, you file for an eviction order.