Custom fields on Branching workflow

Hi,

I am building a custom workflow for for test PWA site. I downloaded code from codeplex and deployed it:

http://projectserver2010.codeplex.com/releases/view/87650

Now, how do I add custom fields and read their values in code behind?

This is a default project information form. I want to add fields to this form (for example "Assogned To"). How can I read that field in the code?