Yes, go to the "Profile" link, near the top, just under where it says "Hello winr1", then towards the left of the screen, click on "forum profile". That will send you to your personal profile page where you can make changes to your profile, including adding an avatar.
If you want to add a picture under your 'signature', which comes up under every post you make, you can hotlink a picture in your "signature" on the same "forum profile" page. The picture has to be hosted on another site, such as Postimage or something similar. Just make sure the picture is correctly sized to a small size, or it will come up as a big picture.
Edit to show you that I just added one. That size is 250x135, to give you an example on sizes. Since Postimage doesn't let you edit pictures the way Photobucket does, I still use my Photobucket account to edit pictures, then just re-download them and add them to my Postimage account to get a decent size for stuff like this.
