I’m trying to configure users to have Yubikeys as an extra layer of protection, we have a Okta SSO working properly, I tried to follow this guide: YubiKey , but I got confused since this setting is a global setting am I configuring my personal yubikey for all user? I notice that there is an option user wise that says yubikey ID but I have not been able to make that work.

Recently all users can be configured to use a YubiKey, the Yubico API key must first be set in the settings. The YubiKey ID is set by pressing the button on the YubiKey in the field which will fill the leading ID from the code. The YubiKey single sign-on mode will prompt users for a YubiKey after login from the web console. The first login will assign the YubiKey to that user.

Oh great that works, I wonder how putting my personal Yubico API, let other people use theirs Yubikeys

A YubiKey is required to obtain a Yubico API key. The Yubico API allows verifying all YubiKeys.