Use of Files in POST Request

[nickallain]

I'm not the world's most technically competent developer, but it would be great if there were an easy way to add a file to an HTTP POST request. I'm fairly certain it's possible with another method (and someone might speak up with a way to do it), but I haven't figured it out. I'm trying to upload a file via the Slack API.
https://api.slack.com/methods/files.upload