YouTube's Dark Theme feature has officially started rolling out to users on Apple's iOS platform. Team YouTube took to Twitter to make this announcement yesterday.
Its finally here! 🙌 Team YouTube (@TeamYouTube) March 13, 2018
Dark theme is rolling out on iOS over the next few days. Toggle it on/off in settings. pic.twitter.com/Mkfl1Dzu3M
As clear from the video embedded in the tweet, you just need to tap on your profile icon, followed by a tap on Settings. Once there, just enable the Dark Theme option, and you'll see the app immediately switch to dark mode.
When asked about the availability of the functionality on Android, YouTube said that's going to happen soon, but didn't provide specific estimates.
Thanks for your interest. Its not available yet, but Android is coming soon!