Sub-Publishers are publishing companies that have agreements with another publisher to administer the publishing rights. They act as an agent on behalf of the original publisher of musical works in a particular territory for a designated term. For example, Sony/ATV Publishing may have an agreement with a publisher in a foreign territory who's responsible for soliciting and collection within that region. In such agreement, the sub-publisher is entitled to a portion of the royalties earned.
If you have a sub-publisher, you can easily add them to your song details using these steps:
Step 1: Once you add your original publisher to the song details, click "yes" where you're asked if the publisher has a sub-publisher / administrator.
Step 2: Search for the publisher's sub-publisher(s) if they've been added to your contacts. If not, click the "Add a New Sub-Publisher" button.
Step 3: Once the Sub-Publisher has been added, select the territory that they control.
If they do not control the USA Only or Worldwide, select "Advanced". Another box will pop up that will allow you to select their controlled territories.
Step 4: Once selected, click Save.
You will then see a count of the territories that were selected.
Step 5: When you've completed filling out the song details, be sure to click Save in the upper right corner before you exit this page.