If you can log in to your Ecunet account:
1. Go to http://sites.google.com/a/ecunet.org/ecunet/ and click the "Ecunet Login" button.
2. Go to https://www.google.com/accounts
3. Click the "Change password" link
You can also navigate to the accounts page from within the mail interface.
If you can't log in to your Ecunet account, fill out the "Sign up for Ecunet" form and indicate that this is a request to change your password.