Note Outlook for Android requires a device running Android 4.0 or later. If the app is incompatible with your device, you can add your mail account by using the mail app that comes with your device. See Set up email using the Android mail app.
Do you have Outlook for Android installed on your device?
If it's not installed on your device, download Outlook for Android from the Google Play Store. Open the app. If you want an introduction, tap Product Tour, or tap, Get Started.
If it is installed on your device, open the app, and then tap the navigation control at the bottom of your device, or tap More > Settings > Add Account.
On the Add An Account page, tap Microsoft 365 if you have a work or school account in Microsoft 365 for business. Enter your full email address, for example tony@contoso.com, type your password, and then tap Sign in.
From here you will see a prompt "Your organization needs you to beef up your security - tap "Enroll"
You will be redirected to a web page, tap Get the app
Install Intune Company Portal by Microsoft, open the app and Sign In
Sign in with your email and email password, click begin > continue > continue > enroll
Tap Allow > activate > OK
At this point you should be on the "Company Access Setup" screen with two green checks next to "Device Enrollment" and "Device Compliance", tap continue > done
At this point we want to get back to the Outlook email setup
open the app, and then tap Settings > Add Account > Add Email Account > Microsoft 365
Sign in with your email address and password and you should be good to go
Once the account is added Outlook for Android will begin syncing.
Also see Microsoft's article at: https://support.office.com/en-us/article/set-up-email-in-the-outlook-for-android-app-886db551-8dfa-4fd5-b835-f8e532091872?ui=en-US&rs=en-US&ad=US