Firstly, install either:
Chrome: https://chrome.google.com/webstore/detail/stylish/fjnbnpbmkenffdnngjfgmeleoegfcffe?hl=en
Firefox: https://addons.mozilla.org/en-US/firefox/addon/stylish/
Secondly, click on the addon in the toolbar and choose "Write style for: www.lowendtalk.com".
Thirdly, grab all of the CSS code from the gist and paste it into the code section of the new window that has appeared. If you are using Chrome, press on "Import" under Mozilla Format and paste it in the pop-up instead.
Fourthly, give Fusl a star: https://gist.github.com/Fusl/fb880ba7ca9d55342856
Lastly, enter any name you wish for the theme (I just called it "Dark Theme"), and hit Save. Close the tab, go back to LET, and it should have a neat dark theme that looks just like this:
