To install...

Users > (you) > AppData > Roaming > Vortex > Themes

Drag the folder to the themes folder.
MAKE SURE YOU INSTALLED THE DELTARUNE FONT INCLUDED WITH THE THEME SO IT LOOKS HOW IT SHOULD!

Click the font, right click, then click "Install" that's in the provided list.

DO NOT PUT THE FONT IN THE THEME'S FOLDER!

If everything is done correctly, it should look like the screenshots.



Enjoy your new DELTARUNE themed interface!