How to Edit Your Name on Tumblrby Jane Williams
When you sign up for Tumblr, the username you choose becomes your Tumblr name and part of your blog's URL. As time goes on, you may realize that this name no longer appeals to you, and would like to change it. You can change this name without losing your followers, by going through the blog's dashboard.
Sign in to your Tumblr account. Open the dashboard of the blog you'd like to edit by clicking the blog's title in the top menu.
Click “Blog Settings” located in the sidebar on the right. Scroll down until you find the URL option. Type your new Tumblr name in this box.
Scroll down the page and click “Save.” This will change your blog's name to the new one.