The following steps will guide through changing your password using webmail.
Sign into your webmail email account. Follow the steps HERE if you need a refresher.
Click Settings in the bottom left hand corner. See below. If your screen differs from below, contact support using the support form on the portal homepage.
Now on your Webmail dashboard, click the Menu in the top right corner (that displays your email address) to open your account settings
Choose Password & Security then follow the prompts to change your password.