Well if you will download Yii framework folder from this link. then you will see a demo application folder also. in this you can check blog application. Where you can see a working example for login form.
Its a very easy and basic approach to start learning yii with this blog application code.
it will gives you a complete overview of yii application and coding.
Once you’ve done with that there is nothing to do here. Go to protected/config/main.php file and change database settings for your application and configure it with mysql database string. Then create tables in your mysql database table. and create models for it.
you can also get a default mysql dump file for blog application in demos/blog/protected/data folder.
Lets try to do some practice with it. You will be fine for sure after some time with it.
So, lets check blog demo app first for all your initial queries.