Before setting up your Office 365 site (known as a tenancy) you should run a check on your educational establishment computers and mobile devices to make sure they have an up to date operating system and browser. You can see a complete list of the technical stuff here.
You might also need to reset your firewall to allow Office 365 to work. Details of how to do this can also be found in the technical stuff section.
You should have the details of your domain name and access to your service provider dashboard, as you will need this for verification of your domain name.