Every new page has the grid turned on already. But you can access the grid settings via the page settings.   Click the Page Toolbar icon (top right corner, next to the zoom bar) Hover over the page Click the cog Scroll down until you reach the grid settings and set them the way you want.  Save   Note: If the grid is set up properly and you still don't see it make sure your image is on the Map layer, not the Token layer.