To enable dark mode in Notion, you can follow these steps:

1. Open Notion and log in to your account
2. Click on your profile picture in the bottom left corner of the screen
3. Select "Settings" from the drop-down menu
4. In the "Settings" menu, click on the "Appearance" tab
5. Toggle on the "Dark mode" switch to enable dark mode
6. The page should refresh and the background should now be dark.

Note: Dark mode may not be available in all Notion accounts or on all platforms. If you don't see the option to enable dark mode, it may not be available for your account or device.