I have never done this so it a good question for me to learn.
We have registered boats from Canada into the USA. But, it different than this.
I assumed it should be something simple if it go through some from of Government. They just make it sound complicated.
When my Ham Radio License came up for renewal, I was getting letters from everywhere to send $10-25 to get my license renewed.
So, I went to the FCC website and read. Downloaded a PDF form and fill it in. I could not find where they say how much money to send?
I called them on the phone and some pretty woman tell me; "It not cost anything to renew. People get your name and address from your 'Call Sign' and try to get you to pay them to do it for you"!
So, I learned two things that day. One, never give out my "Call Sign" on the Internet, just on the Radio as needed. Two, Government stuff is easy if we take the time to learn and ask questions. Heck, I can even keep my Books and do my own Taxes. Weeeeeee!
But, it never hurt to ask and this was a good question for myself.