My Hacker News Dark Theme

hn-dark.js

var link = document.createElement( "style" );
link.type = "text/css";
link.innerText = `
html {
  background-color: #454545 !important;
}

.storylink, .comment p, .comment span {
    color: #eeeeee !important;
}

#pagespace {
    display: block
}
#hnmain > tbody > tr:nth-child(3) > td, #pagespace {
   background-color: #292929 !important;
}

#hnmain > tbody > tr:nth-child(1) > td {
    background-color: #ff5517 !important
}

#hnmain > tbody > tr:nth-child(1), #hnmain > tbody, #hnmain {
    background-color: transparent !important
}

.sitebit, .reply * {
    color: #828282 !important;
}
#hnmain > tbody > tr > td > table > tbody > tr > td.subtext > a:nth-child(7) {
    color: #E6C149 !important;
    font-weight: bold;
}

`

document.getElementsByTagName( "head" )[0].appendChild( link );

Came across this on a HN thread about HN Dark mode. How do I use this?