EAGLE CAD - Enable The Grid

You can put a grid on the screen, both in the schematic and board editor. To do this simply follow the path View > Grid or push the dedicated button placed on the left-top of the editor window.

EAGLE CAD - Access The Grid 

The Grid window appears and allows you to display the grid or not, to select the style of the grid (dots or lines) and the size (value and units).

EAGLE CAD - The Grid Window