Keycloak API - reset password

Question

I would like to use the REST API from Keycloak to reset a password from a user. I have two realms:

• master
• myapp

In "myapp" I have all my users. "master" was only there from the installation. I´m currently struggeling which settings do I need in Keycloak. Which can I use to reset the password / use the API?

If I´m using this I´m getting a error, the user "[email protected]" will not found. I think I need to use realm = myapp ?

String serverUrl = "http://localhost:9009/auth";
String realm = "master";
String adminUsername = "admin";
String adminPassword = "admin";
            
Keycloak keycloak = Keycloak.getInstance(serverUrl, // Keycloak-Server-URL
                realm, // Realm
                clientId, // Administrator-Benutzername
                clientSecret, // Administrator-Passwort
                "admin-cli"); // Client-ID des Keycloak-Admin-Clients
        
UsersResource usersResource = keycloak.realm(realm).users();

List<UserRepresentation>  list = usersResource.searchByEmail("[email protected]", true);

If I change it to

String realm = "myapp";

I got this error message:

Exception in thread "main" jakarta.ws.rs.ProcessingException: jakarta.ws.rs.NotAuthorizedException: HTTP 401 Unauthorized

So I need help:

• How do I setup Keycloak. Which user, which password, which credential settings etc. for using it with my REST API.

Thank you for help