Hi there! Adding an asterisk to a bar chart in Microsoft Excel is a great way to indicate statistical significance. Here's how you can do it:

1. First, create your bar chart by selecting the data you want to use and clicking on the "Insert" tab in the top menu.
2. Choose the type of chart you want to create, such as a column chart or a bar chart.
3. Once your chart is created, click on one of the bars to select it.
4. Right-click on the selected bar and choose "Format Data Series" from the drop-down menu.
5. In the "Format Data Series" pane that appears on the right-hand side of the screen, click on the "Marker Options" tab.
6. Check the box next to "Built-in" under "Marker Type."
7. Choose the symbol you want to use as your asterisk from the drop-down menu under "Marker Style." The asterisk symbol is usually located near the bottom of the list.
8. Adjust the size and color of the asterisk as desired.
9. Click "Close" to apply the changes to your chart.

That's it! Your bar chart should now have an asterisk symbol on the selected bar to indicate statistical significance. Repeat these steps for any other bars you want to mark with an asterisk.