How to create a document and attach it to a specific case

Hi,

I'm trying to send a post request in order to create a document and then attach it to an existed case.

I'm using postman to send a request, the setup looks like this:

https://i.imgur.com/Imm1pF1.png 

The document was created but it doesn't include any files

https://i.imgur.com/BRzoxuE.png 

Can you help me with this case? Thank you!