Add significance indicators to boxplot

Can you provide some examples of what significance indicators would look like on a boxplot? I'm not sure how many of us on here have enough familiarity with extended box plots to know exactly what you are looking for without some help from you to understand.

The other thing that might be important is to know if you are using the built in box plot specialty chart type or if you are building your box plot as a standard stacked column/bar chart. I have found that Excel's built in specialty charts are not very flexible, which makes it difficult to add additional features beyond what the chart can do.