On the top right of every page, you'll see a link to your user page (if you are logged in). That link goes to a page called User:<Your Username>, where "Your Username" is, well, your username. (If you haven't created an account or haven't logged in, it won't work. So go log in.) What should you put there?
A biography is entirely appropriate, but keep in mind that the website is both world-readable and world-editable. That means that anyone can see your page and, more importantly, anyone can edit your page. As a rule of thumb, however, please do not edit others user pages. If you wish to contact them, please user their talk/discussion page.
Beyond a bio, you can turn your page into a blog. Click here for more info.
But these are only suggestions. Your page is your personal space here. Use it as you see fit, but don't be lewd, don't break any laws, etc. Remember, this is a community of those interested in VCU, and we wish to remain as such.