Step-by-step setup of School org
It's easy to get an ArcGIS for Schools bundle, and that comes with your very own ArcGIS org! Your first task is to set up that org. We now have a step-by-step doc that takes you from 0 to a configured, secure org your students can safely work in.
You can find the steps and information in the Quick Start for the ArcGIS for Schools Bundle.
It covers activating your org, securing it, creating accounts for teachers and students, adding another administrator, and connecting with My Esri (and why you want to). Check it out, and share any feedback by commenting here.
Looking for guidance? See ArcGIS Online Organizations for Schools and Clubs. This doc dives deeper how to make the choices and decisions you'll face, while the Quick Start focuses on the steps to take.