This guide can be used with any free or PRO whos.amung.us account.
Login to your tumblr account and go to the "Customize appearance" section.
In the next page, select the "Edit HTML" button.
Now copy the widget code to the part of your blog where you want the widget to appear. We generally recommend that you
find the Sidebar section of your blog HTML code and copy the widget code in there somewhere. Press the "Update Preview" button
at the top to see your changes in your blog. Once you are done press the "Appearance" button on the top left.
Now click the "Save button" at the top of the page to save your settings. The widget is now installed on your blog!