how do you put a cape on a skin

[Wormy21GX]

just wondering how do you put a cape on a skin?

 

[Despacito 2]

There are only four ways to get one.

1. Go to Minecon and get your cape.
2. Donate to optifine and make your cape.
3. Manage to make an amazing realms map and get your Builders cape from Mojang.
4. Use a cape mod.