Enable the Anime Sky in Your Game
Prerequisites
Before the anime sky appears, you need Optifine installed and the resource pack activated in your resource pack menu.
Configure Video Settings
The Sky Anime Resource Pack requires specific graphics options to be enabled:
1. Open Options → Video Settings
2. Locate the Custom Sky option and set it to ON
3. Find Custom Stars and enable it
4. Enable Custom Sun and Moon
5. Close the settings menu
Without these three settings enabled, the anime sky overlay will not render, and you'll see the default Minecraft sky instead.
Activate the Resource Pack
1. Go to Options → Resource Packs
2. Find Sky Anime Resource Pack in the Available list
3. Click the arrow to move it to Selected
4. Position it above other sky-related packs if you have multiple installed
5. Return to the main menu and look up
You should now see the detailed painted anime-style sky with fluffy clouds, stars, or other custom visuals depending on the time of day and weather.