I have a child's polaris 4 wheeler the one with a winch on the front and we bought a new battery but it will not run',its dead.What do I need to check it out so I can order the parts I need?

You never mentioned what model, is this just an electric start problem, will the machine start with the manual pull rope?

"bought a new battery but it will not run',its dead"
You need to start with a Good Battery or more info.