Lines and Shapes in 2-D
Now the fun begins! It's time to draw!

Select the line tool (pencil) from the tool palette and begin drawing a line. To make a single line, click to start the line and drag the mouse, holding down the mouse button, and release to end the line segment. To make a continuous serious of lines, click, move the mouse and click again. Then to continue adding line segments, repeat this process. Make a closed shape. To fully close the shape, you should intersect your final segment to with another line segment -- at an endpoint, a bright green icon will be displayed; at the midpoint, a cyan (blue) icon will show; and anywhere inbetween, a red icon will appear.

You can see and adjust the measurement of your line by watching the dimension box in the lower right hand corner of your screen. You can always manually enter measurements into this box.

If you want to make a more regular shape, use one of the shape tools from the tool palette.

Making it 3-Dimensional
So, how do you make this beautiful shape into a 3-D object? Easy. First, use the select tool to select your shape (if it's a series of line segments, hold down the Shift key while you select each line segment of the shape). Then, choose the push/pull tool and use the mouse to expand and contract and warp your shape. Ta-da! You've created a 3-D shape. If you hold the Control button down while you push and pull, the pushing and pulling will occur perpendicular to the shape which lies flat on the XY plane. In other words, it expands the shape up or down the Z axis. You've taken something in plan view and made it into a digital model.

This is just one way you can make a 3-D object in SketchUp. You can also draw line segments in the 3 axes directions.