In React How to give local css path for grapesjs editor ?

grapesjs.init({
  canvas: {
    styles: ["style.css"]
  },
  ...
})

grapesjs.init({
  canvas: {
    styles: ["style.css"]
  },
  ...
})

where to store that css file ? i mean path to keep that file in react

Depends how you're bundling and serving your pages. For example, if you're serving a build folder, with the CSS in a subfolder there, then use '/css/style.css'.