When, how, and in what form was Catherine of Siena's "Dialog" originally published?

I'm not sure about the book's title also. Here is a link to where you can get a PDF (it's public domain), where it's referred to as "Dialog of Catherine of Siena", but I've seen several alternatives. I've looked on Google and in the introduction to the book itself but I'm just finding dates related to her life. I want to know when people were first exposed to "Dialog", and what kind of medium was used.