The Sitebuilder is a WYSIWYG tool designed for people who do not know how to code sites from scratch or do not wish to do so.
As a result, you are not able to use or upload files in other programming languages such as Javascript, PHP, MySQL, and ASP.
Furthermore, these languages work by delivering and acting upon files that actually remain offsite and stay located on the host server. Given the broad spectrum and possibilities of actions that these languages are capable of, and when combined with the fact that constant input into the Yola hosting servers would be required, there is a degree of damage that could be done and it poses a security and stability threat to the websites of users.
We'd love to help you out though, could you tell us what it is you were trying to achieve and we can see if there is an alternative or workaround that you could implement. Please click on the email link below. If you do require this more complex web designing, then Yola is probably not advanced enough for you at this time.