The legend isn't necessary, the axes aren't labelled, and the title is pretty useless but it's not a bad start. Those are just formatting issues.

First, we'll get rid of the legend. Legends aren't a bad thing, but this one doesn't serve any purpose. First click on the graph itself. Then click on the legend. Once it's highlighted (selected), press delete.

Next, we'll change the title. Click on the graph to activate it, then click on the title to select it. You should be able to put your cursor in the title and retype so that it's whatever you want..

The axis labels take a little more work. When you click on the chart you get two new ribbons: Design and Layout. The Layout ribbon is where we take care of these labels.

To label the x-axis ...

To label the y-axis ...