Once the game loads, click on -> Video Settings -> Shader Packs . Click the button that says Open Shader Pack Folder .
How to Download & Install Insanity Shaders in Minecraft 1.21.6 Download Insanity Shaders Here
: Drag and drop the downloaded Insanity Shader .zip file from your computer's desktop or downloads folder directly into that open folder. Once the game loads, click on -> Video
Before you can run the shader, you will need a shader loader installed for your Minecraft Java Edition: Once the game loads