From Teacher Resources go to Manage Classes then select the class you want to configure and press the Choose class to configure button.
You are led to a form where you can change several things: the name of the class, the school where the class is offered, a brief description of the class, the url of the class homepage, the current announcement, and the version of the class (use a version when you want to make sure the students all do exactly the same homework). The url can be any place where you can store a web page. The most convenient thing is to upload a zipfile containing the webpage, using the upload button at the bottom of the page. Then WHS installs the webpage on the server, and returns the url where it can be found. You type that into the homepage line of the form.
A zipfile for a starter webpage is located at http://www.msc.uky.edu/carl/communicating_math/studwebpg/index.zip
To get started, you can just download this zipfile into the mathclass directory and then upload it.

You will get a message saying it uploaded successfully, and give you the url for the homepage. It will be of the form

http://mathclass.org/Homepages/xxx, where xxx is an integer (the number for Communicating Math is 726)

To modify the homepage,

You can unzip this file into a folder (it will suggest the name index, accept it), then use Word to edit the index.htm file in that folder. When you save it back, make sure you save it as the file type filtered web page (it might also say html only). Then zip it up. You can do this by opening a cmd window (type cmd in the Run line from Start), then typing (in the window)

c: (press enter)

cd mathclass/index (press enter)

zip -r ../index.zip *

A zipfile called index.zip is created in the mathclass folder. Upload this as before, and the changes will be inserted.

Important! Copy the URL see when the zipfile is installed. (It will look like http://www.mathclass.org/Homepages/xxx where xxx is an integer identifier for the class. You can paste this url into the Class Homepage line in the Configure Class table. Then students can access the homepage when they check for announcements after logging into WHS. Note: The class homepage can be accessed without logging into WHS, just point the browser at the homepage url.