Trouble setting Custom Playlist Cover Image

[willreale]

Hello there, I'm having trouble setting a custom cover image for my playlist. I don't understand what needs to go in the body of the request as it isn't listed anywhere in the documentation. Any help would be much appreciated as I am new to this. (https://developer.spotify.com/documentation/web-api/reference/#/operations/upload-custom-playlist-co...)

[Peter_Schorn]

The request should contain a Base64 encoded JPEG image data; maximum payload size is 256 KB. Also set the Content-Type header to "image/jpeg".