HI Betty, this article might be helpful with treating those brown spots - http://www.lonetreevet.com/blog/dog-urine-spots/
Try baking soda. I use 1 cup in a gallon of water every 2 or 3 days.
I spry the lawn where so goes. It's a smallish patch on the side yard so it makes it easier.
water it profusely as soon as you see it- better if it's fresh
Green spray paint
A before a rain, I would rake it so as to loosen all the area which is brown. Let it rain on it to push the urine down and then use top soil and reseed.