Well, if you remember, the idea was that you first do this tutorial and watch the video.
http://blog.contextures.com/archives/2010/03/24/select-answers-with-excel-option-buttons/
This covers how to create two buttons and link them to a cell. You are only interested in the part that changes a cell value either 1 or 2, not in any formulas added later. I can't explain it better than that.
The only difference in this project is that you are linking three buttons (same method) to a different cell. When it works the cell value will change 1,2,3 as you select the 3 different options. The macro looks at the values and gives output accordingly.