Click the Install button on the newly opened window
When it is done, re-open the Minecraft Launcher and the newly installed OptiFine version should be selected already, so click Play
In the Minecraft Menu go -> "Options" -> "Skin Customization" -> "OptiFine Cape" -> "Open Cape Editor"
Here, you can move the cape over to your own (or other) account, and also customize the cape. To customize your cape design, follow these steps:
Head over here and find a cape design that you like.
Then, go here and copy the layers of the cape over.
Now, you can go to the Optifine Cape Editor, hit Banner under the “Design” dropdown, and copy paste the url from the NeedCoolShoes website in.
It will automatically put your banner design in, and then you can hit save.
If you get any errors such as the cape being already moved, or a 24 hour cooldown you can contact our Live Chat support or join our discord and open a ticket to get help from our support agents, we will be happy to help you!