Ah, to set up y'er profile pic, ye first must 'ave a picture to use. With y'er selected picture, I'd recommend posting it to a site like tinypic or photobucket f'er the best quality and resolution. Ye may also post it directly from y'er computer, but 'twill be blurry.
To use a picture uploaded to the internet, right click the picture and click the option that says "Copy image URL". With the URL copied, just paste it in the box provided f'er uploading pictures.
If ye need a more in-depth step by step instructions, I'd be happy to provide ye with it.