Prevent dogs from using on lawn

What you want to do is make your lawn unappealing to dogs. You can do that by spraying smells they dislike (like vinegar) or putting sharp pebbles/rocks around the lawn so they'll stay out, good luck!

If it is your own dog, take them to the area to use. When they use an area you don't want them at, scoop up the poop, have them smell it, have them walk with you and see where you throw it, have them see and smell the scoop again to see it is gone. I have done this with our dogs and granddogs and have no problem with them. Don't scold them just work with them and show them where to go.