LC Lightbox is a jQuery plugin: as first be sure it is already included on your website.
Otherwise download it from here or use the CDN URL like this:
Plugin supports jQuery 1.7 or newer releases.
Then add lightbox core's CSS and the skin you want to use the the site's HEAD:
<link rel='stylesheet' href='path-to-lc-lightbox/css/lc_lightbox.min.css' /> <link rel='stylesheet' href='path-to-lc-lightbox/skins/minimal.css' />
If you want to use touch interactions, you also need to add AlloyFinger on your site.
There's a ready-to-use version in LC Lightbox's LIB folder