How can getrid of weeds.

Pull them out and then spray weekly with weed killer. It took me a year to get a good routine down.
You can buy a gallon plastic sprayer (easy on the hands) and just leave it in the garden. Don't spray anything you don't want dead and don't let your pets out for the recommended time on the bottle. Also check for drying time, so you don't leave your sprinklers on and wash it away or if it rains.
I always buy concentrated and mix myself, it's less expensive.
I usually use 'Round Up' it has a drying time of just 1/2 hour.