Default picture changing HELP

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So I have been on MyLot.com for a while now and although I have practically NO earning to show, I like this site. I joined a while back and then slowly drifted from the site for a few months and recently, as of yesterday, decided to start back up. My question is, I have my default picture from a long time ago on and although I like it, I'd also like to change it. I can't seem to find a place or direction to change my default picture in the help site section. Can you help me? Do you know how?