Go to 'My account' and select 'Stores and imprints'.
At the top left corner, select 'Add imprint'.
Enter the name of your new imprint. This can be the same as your other imprint.
Once you click 'Create', you can edit the imprint details. You can change the personal name
of the imprint to something that describes this imprint the best: this will only be visible for
Scroll down to see the stores. You can set the stores independently.
To add books to your imprint you can either upload new books or modify the books you have
already uploaded. Just change the Publisher / Imprint on the book page.