when you ask "How do I access the default Subversion Repositoy", do you mean where is it located?
In this case, if you didn't modified it during the installation, you will find it in:
where installdir is the installation directory that you configure during the installation process.
If you want to be sure if the project is configured in Trac, you can login to your track and go to Administration > Respositories (under Version Control).
I hope it helps!