To log into the College's instance of Google Apps for Education you simply use your username and password.
Go to https://googleapps.amherst.edu and login using your Amherst username and password. You will be redirected to your Google Apps site. Note that if you have an active login session on another Amherst web service such as Moodle or the Amherst webite, you may redirected automatically to your Google Apps site without having to enter your Amherst username and password.
Go to www.google.com and click the Sign In link. Enter your Amherst email address as your username, but leave the password blank. Click the Sign in button. You'll be redirected to the Amherst login page. Once you enter your Amherst username and password, you'll be logged into your Google Apps site.