Visit the website www.gravatar.com and simply enter the email address you wish to associate with the icon. Gravatar.com will email you a confirmation link which will take you back to the site. The next step will be to design your new icon. You can upload a photo and crop and resize within Gravatar. You can rate your gravatar as ‘G’ or ‘PG’. I always recommend putting up something rated ‘G’ otherwise your gravatar may be blocked on many sites and not displayed anyway. Save, and you’re done!
From this point forward your blog posts will have your new icon attached. If it doesn’t appear it may be because the site administrator (in WordPress) has selected gravatars not to be displayed -they may be replaced with another more generic icon. Administrators can also select to display only ‘G’ or ‘PG’ rated gravatars (all the more reason to upload only ‘G’ rated gravatars).