I just joined this community and decided to start it off good by contributing! I got this guide on another forum and I decided to share it. I didn't write it so please don't ask me any questions.:

1. Go to link removed and login 

2. Once there, click "Cape Code" and enter in one of the codes

Creeper- 47F91

Pig- 29K27

Skeleton- 91A29

Zombie- 29Q35

3. You can only pick one cape and it is permanent, so choose wisely!