Hi there! Creating a simple Yes/No drop down box in Microsoft Excel is actually quite easy. Here are the steps you can follow:

1. Open a new or existing Excel spreadsheet.
2. Click on the cell where you want to create the drop down box.
3. Go to the Data tab in the top menu bar.
4. Click on Data Validation in the "Data Tools" section.
5. In the Settings tab of the Data Validation window, select List from the "Allow" drop down menu.
6. In the Source field, type
   Code:

   "Yes,No"

   (without the quotes).
7. Click OK to close the Data Validation window.

That's it! You should now have a drop down box in the selected cell with Yes and No as the options. When you click on the drop down arrow, you will see the two options listed. Simply select the option you want and it will be entered into the cell.