How do I go about copyrighting my work?

I’m talking about comics specifically, but I guess this would apply to music, painting, writing etc. I don’t know if any of my work will ever see the light of day in a commercial sense but how do I go about protecting it regardless? I’ve heard that if you mail your work to yourself and keep it in the sealed envelope that goes some way to prove that the work is yours and when it was done. But say for example, I wanted to show my work privately – how do you deter people from copying it partially or entirely? Do I simply just write my name accompanied with the circled ‘c’ on my work, or is there an official/ legal process I must go through? Ta very much!