Once the shader pack file is placed in your game's shaderpacks folder alongside a compatible shader loader such as Iris or OptiFine, you need to activate it through your client menus before entering or continuing a world.
Activating the Pack
1. Open the pause menu or main title screen and select Options.
2. Click Video Settings, then open the Shaders or Shader Packs menu.
3. Select Spheres & Physics Illuminated from the list and confirm your selection to reload the rendering engine.
Verifying the Lighting Changes
Load into any biome during daytime to confirm the pack is active. You should immediately notice adjusted sunrays in the sky, upgraded contrast and brightness across terrain blocks, and soft color balances rather than default flat lighting. Because this shader pack maintains the classic blocky look of vanilla Minecraft when used on its own, block shapes will remain standard while receiving realistic lighting and soft highlights.
If you want to tweak how strong the lighting or performance load feels on your hardware, return to the Shaders menu and open the pack's shader settings screen, where you can adjust available visual toggles without leaving your world.