On the top left navigation bar you will see a link called "Edit Mail and FTP Users" click on that.
You will now see an entire list of email addresses you have setup for your domain.
Click on the appropriate email address name that you want to forward mail to.
On the new page you will see a bunch of options.
Click on the tab that says "Mail Forwarding Settings"
Check the box that says "Yes, Forward to Addresses"
Fill in the email address that you want to forward your mail in the box.
(Optional) If you don't want to have the mail saved on the server of your hosting account you can uncheck the box that says "Yes, deliver to mailbox". Understand that by doing this you will only have the mail forwarded to your other account and it will not be saved on your server account. If you are checking webmail or using outlook no messages will appear.