Option #1: WebMail URL
You should receive your username and password via email from support.
Option #2: CPanel Access
You can log into your CPanel.
You should receive your CPanel username and password via email from support.
Under the Email section, select "Email Accounts"
Scroll down to Email Accounts section and next to the email address you'd like to check, click the "More" button and then select "Access Webmail"
Click on any webmail application you'd like to read your mail.
You can try each one to see which one you like the look of better and then optionally, Set as Default your favorite one.