If you have multiple emails or if you are sharing an iPad, it can be useful to add all of them to the Mail app. To do this, navigate to Settings -> Mail, Contacts, Calendars -> Accounts. Click “Add new account…” and you should be able to enter in a new account just like how you did when you set up your first email in the Mail app. Once you’ve got it all sorted out, you should be able to access both email inboxes in Mail.
Have fun with your iPad!