Click on the Zoom out button 
and then click on the top view of the model until the entire model area is visible. Then select the Select objects button 
. First click somewhere outside any of the objects to deselect them all. Then double click on the purple area that encloses the area to be modeled. In the Object Properties dialog box, change its name to "Domain Outline" and check the checkbox labeled Use to set grid cell size and set the Grid cell size to 100. Click the OK button to close the dialog box. Click the Generate grid button 
to generate the grid. In the Generate Grid dialog box, uncheck the Calculate grid angle automatically checkbox and click the OK button.
