Computer Won't Accept Password

Just got a new MacBook Pro and I'm jumping through all the hoops, entering my password again and again for one box after another, and now I'm down to the last one: macOS needs to repair your Library to run applications.

Every time I enter my pass word the box disappears for a fraction of a second and reappears. Same result when I try to cancel it.

Of course, I can't do anything with my new computer until I fix it.