If you are looking to create your line chart you will have to follow a few quick steps to set this up and select your desired metrics.
1. Select the source you want to create the chart for and drag the line chart (or area chart) widget onto the report:
2. Resize your widget to fit your needs by hovering over and dragging it to either side:
3. Click on the chart to bring up the set up menu on the right-hand side and click on the metric to change it:
Please find a detailed video on how this can be achieved: