Log in to your Tumblr account at Tumblr.com.
Click the "Customize" link in the right-hand sidebar to view your Tumblr blog's customization options.
Open the "Info" tab by clicking on it. This displays a number of boxes and options related to your Tumblr blog's information.
Customize the header of your Tumblr blog by creating or editing the current title and description. The description field also supports HTML, which means you can further customize your Tumblr header with photos, videos and HTML-based widgets.
Click the "Save + Close" button when you're finished customizing your header.