Click on Menu at the top of the screen, You'll see a drop down menu that should look like
Go to My Account. Down the left side of the screen you should see
Go to Avatar. There you'll get Avatar: You can upload an image file from your computer to be used as an avatar. Please make sure that the dimensions of the image do not exceed 128 x 128 pixels, and the file size is not bigger than 15000 bytes.
Avatar Galleries: Alternatively, you can choose an avatar from the avatar galleries.
The avatar uploader is beside the top section of writing and beside that is your uploaded avatar.