To generate the ASP WebShell simply click on the button without providing any value in the input box.
Same instruction for the ColdFusion WebShell.
Again nothing special is required of the JSP WebShell
To generate the PHP WebShell choose a password and submit the password through the input box. The WebShell username is administrator by default. To be able to reach the PHP WebShell your user agent need to be set as UniShell. If it is not the case the WebShell will return a 404 on purpose to hide itself.