If you have had a user information in your database, you can use our Login object with authenticate() function to verify user login. We have example in our demo.

It could be that I have not understood fully your need, if so, please let me know

Here is the documentation of Login and authentication

In our example you use AutoMaker datasource, so in the authenticate() function you simply do.

->authenticate(function($username,$password) {
    $users = AutoMaker::table("users")
                    ->where("username",$username)
                    ->where("password",md5($password))
                    ->run();
    // The $users is DataStore object which contain list of user, 
    // something like Collection class in Laravel if you know.
    $user = $users->get(0);
    if($user==null) return false;
    return User::create()
                ->id($user["id"])
                ->name($user["name"]);
})

Above code is just an example of how to use DataSource.

Hope that helps.

Please refer to this answer to know how to create the data connection to your database.