If for any reason you need to add an email account to the Outlook app you can.
1. Select the hamburger icon to open up more options.
2. Select the settings icon.
3. Select Add Account.
4. Select Add Email Account
5. Enter your email address and password just like you did when you first added your email account.
(For those instructions, click here)
6. To navigate between your email boxes, first select the hamburger icon, then select which account you want.