If you have an official Minecraft cape in Java Edition, it can be found in the skins section of the Minecraft launcher. Head to the skins tab, select the skin you'd like to add your cape to ...

The avatars for Figura, the skin mod for Minecraft Java Edition, which are imitated characters who appear in "Blue Archive (ブルーアーカイブ)", the game for mobile devices.

A server-side or singleplayer skin changing mod for fabric.