To learn more about Tags and their usage, check out this article.
To add tags to the questions on your form, navigate to the Settings tab in the survey set up interface...

| ...then click on the Tagging option in the left menu. |
All questions that are on your form will appear on the page.
Open the menu adjacent to each question if you would like to add one or more tags to the question; all tags that have been added for your organization will appear in the list.

Click on Save after you've added tags to your questions. If you navigate away from the Scoring page without saving, your changes will be lost.