Tamirra, you can search around on the internet for sites for young writers. There are a ton of forums and the like where you can post what you've written, receive feedback, and improve your skills. I would not worry about getting published just yet.
Chances are that unless you know someone in the publishing business, no one will even read a manuscript submitted by an 8th-grader. It's a shame, I know, but from the publisher's perspective, there's a 99.999% chance that the work would not be profitable.
PS - You do not *need* an agent. Agents are very useful, but they are not a necessity. If you have written a fun, engaging, or illuminating piece, you'll eventually get it published, agent or no agent. All that publication really requires is the drive to improve your writing and a single original, well-executed idea. (Though agents will of course try to convince you otherwise.)