How to use the auto upload .nzb files feature?

[Suitear]

I want to automatically upload .nzb file after generating it. But can't make it right.

My relevant setting in .ngPost file is as follows.

curl -X "POST" "https://domain/upload-api-full" \
     -F "apikey=*************" \
     -F "nzb=@/home/nzbs/"

Got the following output.

{"status":415,"status_message":"Unsupported` Media Type"}%

So how can I make ngPost automatically upload the .nzb file after it's generated?