Avatar for wordpress blog hosted on godaddy

I have godaddy hosting with wordpress on it as an application. I have been having trouble finding where to add an avatar on my blog? At the moment when I comment on my own blog I dont have a picture however no where have I found the option to “upload picture”. I have also noticed other people who are able to comment on different blogs with their account/avatar but once again I am unsure how to do this. Suggestions?