How to use the distance and area measuring tool: 

1. Click the ruler button in the bottom right hand corner of the screen. 
   
   
   
2. You can change the unit of measurement by clicking "Units" in the bottom left corner of the measure tool dialogue. A pop up will appear, where you can select your units and then click the X in the top right corner.
   
3. To start, click on the map. You'll see an info pop up showing the current area and length of your selection.  
   
4. As you draw your line, the info pop up will automatically show you the length of your current line. In addition, it will determine the area, denoted by the shaded area. 
   
   
5. At any point, you can click the first point to close the shape.
    

That's it. You're ready to start measuring!