Below is some basic information about getting started with Google Classroom. (NOTE: As of 9-14-15, It appears that there is a bug with the version of Google Classroom and/or Google Drive on the iPad that is being remedied, but is not quite there yet. As a heads up it is rather hit or miss right now in using Google Classroom on the iPad.
Google Classroom Quick Start Guide
Workflows that Work Presentation
Google Classroom 101