OAuth JWT Not WOrking

I'm making a POST request, in Postman, to https://login.icims.com/oauth/token with the following body:

audience:https://api.icims.com/v1/
grant_type:client_credentials
client_id:kfitzgerald
client_secret:

- "client_id" and "client_secret" are my username + password used to login to developer.icims.com

I simply receive a 401 everytime:
{
"error": "access_denied",
"error_description": "Unauthorized"
}

How do I fix this? Am I missing something here? Are client_id and client_secret different than your username and password. If so, where do I generate an id and secret to use for the API?