MyDraw drawings are equipped with a grid patter by default, which is aligned to the horizontal and vertical rulers on the page. Not only does this allow for precise sizing and alignment, this function also enables the Snap and Glue functions to help you align a drawing's shapes perfectly.
To change the units and drawing scale, see the Drawing Scale topic. To zoom in or out, which will either decrease the step size of the ruler and simultaneously increase the percieved grid size, hold Cntl+Scroll Up, and to increase the step size and decrease the grid size hold Cntl+Scroll Down.
Alternately, you can go to the View ribbon tab and choose your zoom factor from the Zoom area.
To manipulate the grid to your exact specifications, go to the View ribbon tab and click on the Grids and Rulers button. This will open up the Grids and Rulers editor.