EzExposure is a shader pack, so it runs through a shader loader such as Iris or OptiFine. Once it is active, it gives you an exposure slider for controlling how bright the world looks.
Activate the shader pack
1. From the title screen or the pause menu, open Options, then Video Settings.
2. Open the shader menu. Iris calls it Shader Packs. OptiFine calls it Shaders.
3. Select EzExposure from the list of packs.
4.
If the pack does not appear in the list, check that it is in your shaderpacks folder. You can open that folder from the same shader menu.
Open the exposure setting
1. Stay in the shader menu with EzExposure selected.
2. Open the pack's settings. In Iris this is Shader Pack Settings. In OptiFine it is Shader Options.
3. Find the exposure slider. It is the main setting this pack adds.
4. Drag the slider and apply the change. Then return to the game to see the result.
The pack keeps the normal vanilla style. Expect the same familiar look, just brighter or darker. Don't expect dramatic shadows or water effects.
You can come back to this menu whenever you like. Adjusting exposure takes only a few seconds, so tweak it as often as you need.