Fork the hack-night (https://github.com/rubyloco/hack-night.git) on github to your account (ala https://github.com/shadowbq/hack-night.git)
Using the shell download your clone, create/switch to your topic branch, add your submodule, commit it, push it to your account.
git clone https://github.com/shadowbq/hack-night.git
cd hack-night/
git remote add upstream https://github.com/rubyloco/hack-night.git
git fetch upstream
git checkout -b shadowbq-loco-flag upstream/master
git submodule add git://github.com/shadowbq/shadowbq-loco-flag meetings/2015-07-13/shadowbq
git status
git commit -m 'added my submodule'
git push origin shadowbq-loco-flag
Go to https://github.com/shadowbq/hack-night and select your feature branch.
Click the 'Pull Request' button and fill out the form.