How do I install a Tumblr theme?
1. Open the HTML file in a code editor like Notepad, Text Wrangler, Sublime Text, Atom, etc. (do not double click because that will open it in the browser).
2. Select the whole text and copy it.
3. Choose your blog in the Tumblr dashboard.
4. Click the Edit theme button and then click on Edit HTML.
5. Select all the HTML code and replace it by pasting the previously copied code.
6. Click Update Preview and then click Save.