To add a calculated field to a specific section in a Microsoft Forms form:

1. Open the Microsoft Forms form that you wish to add a calculated field to.
2. Select the section to which you would like to add the calculated field.
3. Choose the Plus icon and select Calculated from the options.
4. Type in your calculation formula within the provided box by entering the names of the fields you wish to add up.
5. Click Add to save your calculated field.