The ucla/polymer generator will automatically drop an appopriate .gitmodules file in your dir
To add to an existing project
git submodule add https://github.com/ucla/ucla-iam-core.git app/styles/ucla-iam-core
Which will create a .gitmodules containing
[submodule “app/styles/ucla-iam-core”]
path = app/styles/ucla-iam-core
url = https://github.com/ucla/ucla-iam-core.git
Feel free to change app/styles/ucla-iam-core in the command if you wish it elsewhere.
Once installed you can pull down the latest version inside your application by running
git submodule update --remote app/styles/ucla-iam-core