Googy Shaders works with both Iris and OptiFine setups. Once the shader archive is in your game directory, you can turn it on directly from the pause menu without restarting Minecraft.
Placing the Pack in the Shaderpacks Folder
1. Launch Minecraft with either your Iris or OptiFine profile and load into the main menu or a world.
2. Press Esc and open Options, then click Video Settings.
3. Open the Shader Packs menu (in Iris) or Shaders menu (in OptiFine).
4. Click the button at the bottom of the screen to open the shaderpacks folder on your computer.
5. Move your Googy Shaders file directly into the shaderpacks folder without extracting its contents, then return to the game window.
Turning the Shader On
1. Look for Googy Shaders in the list on screen.
2. Click its name to highlight it. In Iris, click Apply at the bottom so the game reloads its renderer; in OptiFine, clicking the pack name loads it right away, after which you can click Done.
3. Unpause your world to view the updated lighting, smooth block shading, and animated foliage.