There are probably other ways to change your picture (the "Mystery Man", but here's the one that I used.
Visit http://www.gravatars.com and set up an account using the email address associated with your blog. Upload the image you want to use.
Now whenever you visit ANY site, when you log in with that email address, your picture will show up with your comments. Including in your forum question above, if you've used the same email address to register here.
On your blog Dashboard, go to Settings > Discussion and enable the avatars at the bottom of the page for your commentors' avatars to display.
As far as viewing your profile page on your website, I'm not sure about how to associate it with your "About" page specifically. But all you have to do is click on the "About" page, at the top of the page - once you have edited its generic contents from the Dashboard.
Hope some of this helps (and I stand to be corrected - I'm a newbie too)! Cheers.