It’s intentional that there’s no mention of Sidekiq there, this is all supposed to work magically in the background without any action on your side. We make sure that it does.
The fact that it’s not working on your site points to a problem in your configuration.
It’s difficult to diagnose what the issue is without much context. So Please try to provide as much information as you can.
can I get a link to the site you’re having trouble with?
can you try safe-mode?
are you using Cloudflare?
do you see any errors in the browser console on pages with images that are supposed to be lightboxed?
do you see anything unusual in your.site.com/logs?