In the Chart Options section, select the Legend checkbox.
In your presentation, click the legend to select it, then do any of the following:
Change the look of the legend text: Click the Style tab at the top of the sidebar, then use the controls to add a background fill, add a border, and more.
Resize the legend: Drag the handles around the legend.
Reposition the legend: Drag the legend to where you want it.
Tip: To position the legend more precisely, select it, then press the arrow keys on the keyboard. To move the legend in larger increments, press and hold the Shift key while you press the arrow keys.
Axis lines define the edge of the chart, sometimes also marking the zero value, like an inner border. Evenly spaced gridlines cross the chart and provide a visual reference for large increments in the values. You can specify whether to show chart axis lines and gridlines and modify their look.
Click the chart.
In the Format sidebar, click the Axis tab, then click the Value button near the top of the sidebar.
Click the disclosure arrow next to Reference Lines, then choose any of the following types of reference lines from the pop-up menu:
Average: A line that runs through the mean value of the data
Median: A line that runs through the middle value of the data
Minimum: A line that runs through the lowest value of the data
Maximum: A line that runs through the highest value of the data
Custom: A line that runs through a value you specify