Hi @phearin
I'm not familiar with BOX but normally when uploading a file using flow you need to use a similar format to the one below. This example is from uploading to Jira but should work anywhere where the 'file' option would work in Postman

{
"$content-type": "multipart/form-data",
"$multipart": [
{
"headers": {
"Content-Disposition": "form-data; name=\"file\"; filename=XXXXX"
},
"body": XXXXX
}
]
}The 'body' should be the file content you get when retrieving the file.
Hope this helps,
Sam