Every content item in your Authory account is allocated to a source/publication. As in, you import an article from, say, the publication "TechCrunch", and for this article and all future articles that you import from there, you create a new source called "TechCrunch" in your Authory account.
The source is visible on your portfolio in the meta line of every content item:
Once a content item has been imported, it's not possible to change the source/publication that you've added it to.
If you want to add the content item to a different source, you can delete it and import it again, this time adding it the source that you prefer (or creating a new source for it).
While it's not possible to change the source for a content item after it's been imported, you can change the name of the source anytime. Here is how