As an independent author, you are your own publisher. Your imprint is the name of your publisher. It can be your name or any other name you would like.
In Bowker, visit My Account > My Profile Data > My Company menu. Scroll to the bottom and add the name of your new Imprint.
If you use a free ISBN from KDP or IngramSpark, you will not name your imprint. Your imprint will be listed as “Independently Published.”