jira integration - add an attachment

Has anyone managed to get adding attachments to a jira issue to work via the rest API's ?
I can happily create an issue and update the custom fields etc, but have yet managed to do the above. From reading the API docs, the process is two staged : 

1) create the issue and get the new issue key ( /rest/api/2/issue")
2) attach files using the above key.(/rest/api/2/issue/17913/attachments")

When I try to attach a file I'm getting 
Failed to connect to jira.BLAH.com/.../attachments HTTP/1.1 415

I'm using the same auth details as when im creating the issue and have updated the header as per the API docs to include X-Atlassian-Token