You need this to get it done:
Action DetailsRequirements and how-to articles for Tumblr's action:
The email address you wish you be associated with your Tumblr account. This is where your verification email will be sent.
Blog Title and URL
Email address, password and a unique username. Usernames are in all lower-case and can only contain letters, numbers and dashes (no spaces.)
Usernames are in all lower-case and can only contain letters, numbers and dashes (no spaces) (maximum of 32 characters.)
Choose one of Tumblr's available themes and once you've found one you like, install it on your blog.