Mysql nagios plugin where do you store the user and password

I have nagios setup to monitor multiple mysql servers, and it just works already.

I’ve setup a new environment, and am getting:

User does not have access privileges to database: Access denied for user ‘nagios’@‘localhost’ (using password: YES)

Where is the username and password stored? or what is the default username and password I’m supposed to use?

I’ve compared the users between databases and created them identical but still not working.

I appreciate any thoughts.