First of all, if your server requires only a Kerberos authentication and not also a NLTM authentication, make sure that you have configured NeoLoad for Kerberos.
For more information you can check the NeoLoad documentation here
You will have to fill the krb5.conf with your Kerberos server information. You can capture the network traffic without NeoLoad to check the Kerberos information needed.
When it's done, in your script, at the server level, you should add your Windows credential in that format: DOMAIN\username and your password under the login and password column.