How to do this depends on which story format you're using (SugarCube, Harlowe, Snowman, etc...).Update the tags or the text of your message noting which format of Twine you're using and then we'll be able to help.(Personally, I prefer SugarCube.)
Alternatively, you can take a look in the "Twine Cookbook" at the "Cycling Choices" section. They have sample code for this for the three story formats I listed above.