You'll also need the building measurements and your floor plan sketches for reference.
To start, you'll go to the Menu bar, and select Camera --> Standard --> Top. This will show you an overhead, or bird's eye view, of the ground. Next, go back to Camera, and select Parallel Projection from the drop down menu. This will give you an accurate 2D-like view. Because SketchUp is more intuitive in this angle, Parallel Projection also helps you draw precise lines.
Using your Line tool and your physical measurements, begin drawing your floor plan. Remember, to draw a line; do not drag the mouse. Click point A and then point B because SketchUp performs better this way, and you receive more accurate results. As you are hovering the mouse, you will notice the Value Control Box (VCB) in the lower right hand corner recording your measurements. You can choose to physically control the VCB with your mouse. Or, you can click an approximate point B, and then type the precise measurement and select enter. The line will automatically reconfigure itself to match your precise measurement.
After you have drawn all the outer walls of your house, it's time to draw the inner walls. First make sure that all the lines are connected and closed. The lines will transform from a thicker line to a thinner line once closed. Now, select all the lines of the outer walls. Click on the Offset tool (or F on your keyboard), and create an identical inner wall inside of your outer wall. Type in the exact measurement of your inner wall offset in the VCB. Outer walls are generally no thicker than 12 inches.