Putting a modified submodule in your repository on Github

I am working on an assignment for a class where my professor has created a fork of MIT’s xv6 OS and I need to work with a partner on the assignment through github. So I set up a private repository to do it and I put the xv6 I was working on inside of a parent folder. Now I added the submodule to .gitmodules and the only problem is I don’t know how to set up the submodule in .gitmodules in order to get my local xv6 rather than my instructors fork so my partner can see what I am doing.

Git Baby is a git and github fan, let's start git clone.