To add a new email account to a existing account log into Telstra My Account.
Click on Manage your email accounts on the left hand side under Plans and usage.
Click on "Add Mailbox"
Type in the user name you wish to use and click on "check" to make sure it hasn't already been taken.
Type password you wish to use for the account in password field.
Retype password in the Re-enter Password field
Click on confirm.
The new email account should be set up.
Can test the new email account at WEB Mail
If can't see "Manage your email accounts" Check that the account for your Bigpond Internet is selected in Drop down list top centre of page
To configure email account in an email client on mobile device, PC or MAC see.