Go to the LTI/LMS area in the course you wish to integrate to Google Classroom.
Select Connect to Google Classroom and authenticate to your Google account.
When authenticated you will be redirected to the Classes List page and will see a list of your Google Classes.
Select Connect Class button for the Google class you wish to connect your Codio course to.
Your Codio Course is now integrated with your Google Class.
Note
Google classrooms do not support the ordering of modules/assignments from the Codio Course, they will be generated randomly but can easily be reordered from the Classwork tab in your Google Class