Download the OptiFine installer for your Minecraft version from the official OptiFine website
Make sure you have Java installed (Java 8 is typically required for older Minecraft versions)
Double-click the OptiFine jar file you downloaded
Select the Minecraft version you want to install, if prompted
Click Install
Open the Minecraft Launcher
Go to Installations
Select your Minecraft profile (or create a new one for that version)
Click the dropdown for Version and select the OptiFine version (e.g., “OptiFine 1.xx.x”)
Click Save (or Create)
Click Play using the OptiFine profile
If OptiFine doesn’t appear, verify the Minecraft version matches and that the OptiFine installer completed successfully