Fortunately, you can use Tumblr's HTML editor, located on the Customize page, to change the ... third-party Web font you must add an extra block of code attaching the font's CSS to your theme.

When you change ... CSS file to your Tumblr account. Tumblr will display the URL address for the new file once the upload is complete. Copy the URL address for the CSS file and return to the HTML ...

Where HTML defines the structure and content of a web page, CSS (Cascading Style Sheets) is the coding ... line will change the typeface on all pages to Arial: html body { font-family: Arial ...