Return to your Minecraft window. You will see the Fullbright pack appear under the "Available Resource Packs" column on the left. Hover over it, click the arrow icon to move it to the "Selected Resource Packs" column on the right, and click .
To get "Fullbright" on Minecraft 1.8.9, you can use a resource pack to permanently light up the world, allowing you to see in caves, at night, or in the Nether without torches. Recommended Resource Packs for 1.8.9 fullbright resource pack 1.8.9