Measuring distances along a path (line), areas (within a polygon) and coordinates is accomplished by opening the toolbar on the top left corner of your project. 

Click on the "measurement tools" button and note that there are three buttons corresponding to area, distance and coordinates respectively. 

Click on one of the three tools and then click on the map to begin your measurement. Note that you may change the units of your measurement at any time. The image below shows a distance measurement in miles. You can also measure distances in kilometers, feet, meters and yards. 

To view a video of using the measurement tools, click on the following image: