Go to your Control Panel (CP). Select "Edit Avatar" from the menu on the left side. When you get to the next screen, it will allow you to put an image in the avatar "box". You can select a "canned" image, a URL image, or one from your computer.
Your image is restricted in size to something like 80 X 60 pixels, so you may have to edit or re-size it with a photo editing program before uploading it.
I don't know if you are restricted in doing this until you have a certain number of posts.
My wife and I are huge fans of bears, gorgeous creatures. We adopted the bear paw as our business logo. It makes a powerful statement to me, I remember the first time I came upon a bear track, I had not seen a wild bear at the time. The bear had been around my salt lick and I have to say it sent a chill up my back to see the size of the track and the earth it moved from scratching. They are powerful majestic beast