Download Optifine

Start by downloading the appropriate version of OptiFine for your version of Minecraft from this link.

Step 2

Activate the Installer

Click on the installer you just downloaded, which will automatically install OptiFine for Minecraft. It will also create a profile in your Minecraft launcher called "Optifine."

Step 3

Start Minecraft & Select Optifine Profile

Open up your MC launcher and select the Optifine profile.

You'll know that it's working successfully when you see the name of the profile in the Minecraft screen.

For more information, check out the video guide below from SexyPurpleUnicorn: