In synchronous modeling, the grid is displayed only when you are using a command that adds or edits drawing elements, dimensions, and annotations.
Choose the Grid Options command 
.
In the Grid Options dialog box, set the Show Grid option, and then click one of these display options:
As Points
As Lines
In the Grid Options dialog box, select these additional sketching aids:
Show Readouts option--To display X and Y coordinates relative to the current origin point.
Show Alignment Lines--To display alignment lines as you draw.
Snap To Grid, plus one of the following options:
To draw lines that snap to the grid intersections, select the Using Points option.
To draw lines that snap to the grid lines, select the Using Lines option.
Choose any drawing command.
As you move the cursor to begin drawing, the grid displays the coordinates of the current cursor location in relation to the origin point. To provide precision input to the current command, click when the coordinate display indicates that the cursor is in the correct position.
Tip:
You can use the Reposition Origin command to move the user defined origin point as often as needed. This is helpful when you want to:
Draw or place 2D elements at exact locations.
Draw or place 2D elements at exact distances from other elements.
Keep dimensions horizontal and vertical on coplanar faces or edges at different orientations.
You can use the Zero Origin command to reset the origin to the (0,0) coordinate of the drawing sheet or reference plane.
In synchronous modeling, you can use the Zero Origin command to reset the user defined origin to the center of the sketch plane (0,0,0).