How to show a field based on users answers.

I would like to create a dropdown where the question is either yes or no, but if they choose yes then a box would drop down so they can fill in their information.  If they choose no then it just moves on.

Thanks

Looks like you are looking to show fields based on users selection, please check this guide: https://www.jotform.com/help/316-How-to-Show-or-Hide-Fields-Base-on-User-s-Answer 

Let us know if you need more help.