Admin Settings
You can turn off login alerts for all users and agents by heading to Sidebar Menu → Settings → General
And on that page, search for User Login Alert and from drop-down select Disabled and save changes.
User Settings
If an admin has enabled this option, then an individual user can turn off login alert notification.
Go to Sidebar Menu → Profile → Notification Settings, select disable for login alert field and save.
WhatsApp Agents:
Master agent can turn off agent’s login alert notifications by editing agent’s profile, select disable for login alert field and save.