Hi,
If you want to develop on mojoPortal, you will need to get the source code. What you have, that was installed by the Web Application Installer, are the release files. The release files do not have solution or project files.
To get the source code, please read this documentation: http://www.mojoportal.com/getting-the-code-with-tortoisehg.aspx.
HTH,
Joe D.