Create a public upload on your account with the specified parameters. Don't forget to specify POST as the request method as GET will call the list action rather than create.
https://streamio.com/api/v1/uploads.format
POST
201
Here's an example of creating a low bitrate (around 300k) profile.
curl -u username:password \
-F title=SpringCampaign \
-F tags=Community \
https://streamio.com/api/v1/uploads.json