How do you add an additional format or file to an existing post?

You can add more formats to a post by clicking the "Edit" button when you're viewing a video. You can find the "edit" option on both the episode page and the blip.tv dashboard.

Then click the "Add additional format" link. Browse to the file you want to upload, select it, and when you're done click the "Update" button at the bottom of the page.