Open Outlook for Android. The icon looks like this:

Outlook for Android 

If you haven't already, you can download Outlook for Android from the Google Play Store.

STEP 2: 
Tap Get Started if it's your first time.

Or, go to Settings > Add Account > Add Email Account.

Go to Settings 

Select Add Account 

STEP 3: 
Enter your full email address, then tap Continue.

Enter your email address. 

Enter your email account password and tap Sign In or Next.

Note: The sign in screen may look different for you depending on your email provider.

Enter your password for your email account. 

STEP 5: 
If you have 2-step verification turned on, identify yourself using the method you chose (6 digit code, phone, or using the Microsoft Authenticator app.

STEP 6: 
Outlook may request permission to access your calendar, contacts, etc. Tap Yes or Allow

You're now ready to use Outlook for Android!