Adding any Multi-Factor Authentication (MFA) provider into Clearlogin can be found here https://admin.clearlogin.com/mfa_providers. This will list your current MFA providers and allow you to add new ones as well.
Currently Clearlogin only supports one MFA Provider at a time, so if you have another MFA Provider you are switching from you must delete it before adding the new one.
Click on DUO MFA
Go to https://admin.duosecurity.com login and select Applications on the sidebar. Click Protect an Application and add Auth API.
Then note your Integration Key, Secret key, and API Hostname. In the details section of this page.
Enter your Integration Key, Secret Key, and API Hostname which you had noted earlier and click Save.
Congratulations you are now using Duo as your MFA provider!