Well,firstly read the rules and post an introduction telling us about yourself, then you're good to go.
Now here's how to post your work. First, make sure your work is saved as a .gif or .png file.
Then join an image-sharing site. Photobucket, Imageshack, or similar sites only take a few seconds to sign up to. Upload your work to there and then copy the IMG code underneath it (or near it) it starts with [IMG]. Paste the code into your post and your work should appear just like magic!