1. Download Optifine for the Minecraft version (e.g R.A.D uses 1.12.2)
  2. Open mods/ folder located in the modpack’s directory.
  3. Copy the Optifine .jar into the mods folder. THERE IS NO NEED TO OPEN THE JAR OR RUN IT
  4. Start the client with the desired modpack so Optifine creates its folders
  5. Put your preferred shaders .zip file in shaderpacks/ folder and then choose shaders from in-game options menu.