To add an AutoShape

On the Insert tab, in the Illustrations group, select Shapes.

Click the shape you want from the drop down menu. Click and drag to insert the shape you want.

To draw a circle or square

Click Oval or Rectangle on the toolbar.  Click and drag to insert the object you want.

Tip - To maintain the shape's width-to-height ratio, hold down SHIFT while you drag the pointer.

To add a line

On the toolbar click on the line.  Click and drag the line to the required length. 

Tip - To draw a straight line hold down the Shift key while dragging the pointer.