Brand Registry is the door to A+ content, brand analytics, and the tools that remove hijackers from your listings. It used to require a registered trademark. Since the pending-application change, a live application at an accepted office is enough.
That sounds like the hard part is over. It is not. The hard part moved from "wait for registration" to "file something that will not be refused".
Why applications get refused
Trademark offices refuse for two main reasons, and both are checkable before you pay the filing fee.
The first is that the name is descriptive. "Soft Cotton Socks" for socks will not register anywhere. Amazon will still enrol the pending application, and then the refusal arrives and your enrolment is at risk.
The second is that someone already owns something too close. Not identical, too close. "Lumina" will be refused against "Luminna" in the same class. "Kwik Fix" against "Quick Fix". Offices search similarity, sound and meaning. Sellers usually search the exact string and stop.
The check that saves the filing fee
Type your name into the search above. It runs the same kinds of comparisons the examiner will: exact, similar spelling, same sound, other alphabets, across 85 registers. Set the class to your goods and the territory to the office you plan to file in.
If the top results are live marks in your class with a high score, pick another name now, while it costs nothing. If the nearest marks are dead, in different goods, or far apart in spelling, you have a name worth filing.
The order that works
Search, then file, then enrol. Sellers who enrol first and search never tend to find out about the conflict from the refusal letter, or worse, from the other owner's opposition. By then the packaging is printed.
If you file in the United States, use the classes your products actually sit in. Class 25 for clothing, 21 for mugs and kitchenware, 9 for electronics, 16 for books and paper. Amazon's own categories do not map to Nice classes one to one, so check the class page for your product before you fill in the form.
And keep your filing details somewhere safe. Brand Registry asks for the serial number, the owner name exactly as filed, and images of the mark in use. Mismatches between the application and the enrolment are the second most common reason approvals stall.