Knowing someone always helps. That point aside, you might consider starting off small at local/State conferences. If people enjoy your presentations, you will likely be contacted by event organizers, or they will at least know of you when you contact them. You might also consider organizing your own local conference. Contact your local State director for one of the certifying organizations.
Contact the specific organization whose conference you would like to participate in. They will generally have written guidelines and requirements for you to peruse and see whether you qualify to serve as one of their presenters. Assuming that you do, then you can pose your seminar/workshop idea (of course following the specific format that they require). If they like it, they will contact you.