I don't know where you live, Sweetie Girl, but where I live about once or twice a year Disney reps come to Washington DC, which is about 30-45 minutes from where I live, and they send out promos like commercials on the radio and stuff saying kids between the age of 9 and 16 who are interested in singing, acting, dancing, etc. are wanted for Disney channel, and to call a certain number to secure an audition.
That's one way to do it, but of course if you don't live somewhere where they do it, then it wouldn't work. Plus, I think these casting auditions are for smaller parts like guest roles. But that's the way to start, I believe. Get out there and show them what you've got, and some day maybe you'll actually get your own show.
Just remember you can do anything if you try, but don't have extremely high expectations. One of the things actors go through the most is rejection for roles and stuff.
So do what Lauren said
get involved with theatre in your community, and once you are old enough to have a school theatre program (high school, most likely, and possibly middle school, not sure) be active in that! If you are serious about it, practice as much as you can get, look in local newspapers for actor workshops, drama classes, stuff like that.
But don't give up! Take the next step toward your goal, whether that's just getting involved, contacting an agent, or whatever.