Hi @vijeth kharvi ,
Thanks for reaching out.
The Authenticator app is not available in your tenant because it has not been enabled. To enable the Authenticator app for your tenant, you can navigate to Azure Active directory->Security->Authentication Methods
Select Multifactor Authenticator and enable that for all users as shown:
Also, you can navigate to Azure Active Directory->Users and Select Per-User MFA which will redirect to MFA page.
Go to user settings and select the check box 'Notification through Mobile App' to get notification through Authienticator app.
Hope this will help.
Thanks,
Shweta
Please remember to "Accept Answer" if answer helped you.