Here are the steps on how to turn on light mode in Discord:

Desktop

1. Open Discord.
2. Click on your profile picture in the bottom left corner of the screen.
3. Select User Settings.
4. Under App Settings, select Appearance.
5. In the Theme section, select Light.
6. Click Save.

Mobile

1. Open the Discord app.
2. Tap on your profile picture in the bottom right corner of the screen.
3. Select User Settings.
4. Under App Settings, tap Appearance.
5. In the Theme section, tap Light.
6. Tap Save.