Change your site address
Open Menu, then WEBSITE, then My website, and find Site address at the top.
Type the name you want in the Address box. This is the part that makes up your public link. If someone already has it, the screen says "Already taken. Try another."
Tap Copy link to grab the finished address once you are happy with it.
Worth thinking about before you change it: anything you have already handed out, printed, or linked from social will point at the old address. Change it early rather than often.