Where to start? With an idea! Anim8or is a means to an end, the end is up to you. A tip: Think big. Bite off more than you can chew, and chew like crazy!
What I'm trying to say is have a think about what you'd like to create (still shot, game element, animation, Star Wars episode 8 ), and go about creating it with Anim8or. To do that you'll need to know the basics, so spend some quality time with the manual (it's very, very short for a system manual) and if you feel inclined run through some of the tutorials. Then experiment, play, try, fail, try again, succeed, learn, develop, improve, all of which is the fun part. While becoming awesome at Anim8or-fu, if you have any questions try searching the forum first (because most likely someone will have had the same question at some time) and if no luck, post a thread.
Most importantly: enjoy the process. Welcome, and good Anim8ing!