Go to www.howeisd.net, click on Clever, and login.
Once you are logged into Clever, you will click on McGraw-Hill and be taken to a page that looks like this:
Click on "Create a Class" or "Redeem Content" and start building your class for your students to have access to their content.
You will be able to create a class, set a start/end date, and make a class name. Obviously you will not be able to do this until you get a class roster, but you are still going to be able to look around your content, etc.
Please let me know if you have any questions!