Edit the file config/db.php
with real data, for example:
return [
'class' => 'yii\db\Connection',
'dsn' => 'mysql:host=localhost;dbname=test',
'username' => 'root',
'password' => '',
'charset' => 'utf8',
];
You must install Yii 2 (/vendor dir) before use project.
You must apply migrations before use project.