Terms Of Use: https://mistifonts.com/flame-fetish/

To create a swash: Type the word, then type underscores until you have achieved the desired length.

Note: You need to have ligatures turned on in your chosen program! These swashy underlines are also available as PUA encoded glyphs, so you can use them in any program! More information on that here: https://www.creativefabrica.com/the-ultimate-font-guide/pua-encoded-fonts/