Try these links
It is also possible to create a blank form from a dashboard assembly then modify it from there.
There are step by step instructions in the Epicor Customization Users guide for the version you are on (Classic). In earlier versions of the online help there were pdf copies that you could download, looking at the latest version they don’t appear to be there. If you are struggling to find the information in the help then you can try on Epicweb here You will need access to Epicweb