The conventional way of setting up Dark Mode is done from the Settings app. Browse for Display & Brightness and right at the top of the screen, in the Appearance section, you can easily switch between Light and Dark themes. The Light theme is the usual interface that you’ve been used to, in all the previous years without a Dark mode. On the same Settings page, you can allow iOS to automatically switch between the two modes, according to your local Sunrise and Sunset.
iOS 13 Dark Mode Control Center Toggle
If you would like to keep things manual and decide when to switch between Light and Dark modes you can simplify things by enabling the Dark Mode Control Center toggle. A single tab of the button will enable and disable the Dark them. This is done in Settings -> Control Center -> Customize Controls. Here you can add Dark Mode switch. Drag it to the desired position in the Control Center list.
How To: Swipe for Control Center and tap the Dark Mode icon to enable or disable!
Hidden Dark Mode Shortcut In Control Center
If you did not manage to configure the Dark Mode toggle in the Control Center, there’s still an easy way to enable or disable this new theme, thanks to a hidden shortcut in the Brightness control bar:
1. Swipe for Control Center.
2. Long press the Brightness control bar.
3. Tap the Dark Mode icon to enable or disable.