Making your Tumblr blog private is easy, and it can be done in just a few simple steps.
1. First, open up the blog in your browser.
2. Click on the three lines in the top left corner of the blog page.
3. Under “Layout,” click on “Customize.”
4. In the “Customize” window, click on “Privacy Settings.”
5. In the “Privacy Settings” window, under “Public,” click on “None.”
6. Click on “Save Changes.”.