If you want your Tumblelog to be private, only letting access to the people you choose, there’s a feature called password protect.  So you can now share your blog only with friends, family or classmates. (by tumblring)

IMPORTANT: You cannot password protect your main Tumblr blog, only secundary blogs.

1. First of all, go to your SETTINGS and then select the blog you want to protect.


2. Go to the end of the page and you’ll find the Password section. Now, what you have to do is click Password protect this blog and then choose a password to your Tumblr. Save and it’s all done.