My understanding is that as a creator, you do not have to register your work for copyright to be in effect.
Protection is automatic on creation of the work.
However, if you fail to reister within three months, your right to statutory damages may be lost and you may be limited to actual damages. You do have to register your copyright before initiating a lawsuit to collect damages for infringement. Following are some excerpts from the visual arts department of the copyright office. The owner of copyright in a work has the exclusive right to make copies, to prepare derivative works, to sell or distribute copies, and to display the work publicly. Anyone else wishing to use the work in these ways must have the permission of the author or someone who has derived rights through the author.