You can setup one or more email accounts to collect and print your emails. You can access your email account in both Apple Mail and PrintDirect at the same time.
Tap on the 3 lined button in the top left of the screen to open the left side panel. Tap on "Email" to show the email screen and then tap on "+" in the top right to add a new account.
Enter your email address and password to search for your account settings, or tap on "Manual" to choose the account type yourself.

You can delete email accounts by swiping left over the account name or tapping on the settings (cog) button beside the account then tap on "Delete Account"