Article: It's a white app with the red YouTube symbol on it. If you're signed in to YouTube, doing so will open your YouTube Home Page. If you aren't signed in, tap the gray profile icon at the top-right corner and select Sign in to do so now. You'll find this in the top-right corner of the screen. If you haven't yet assigned yourself a profile picture, you'll instead see a person-shaped icon or the first letter of your name here. It's one of the options under the "YOUTUBE" header. As long as this switch is on (green), all potentially mature content, including foul language, will be blocked for this account on your iPhone or iPad.

What is a summary?
Open YouTube. Tap your profile picture. Slide the "Restricted Mode" switch to On .