You need a web server of your own on the Internet to publish your app.
You can select one that suit your needs from a very wide range of services that rent you a web server, but probably a small and inexpensive VPS or a shared hosting will be the best choice for you now.
The rest of the process depends much on the service that you select. Usually it involves setting up of a linux server which requires you some knowledge.
[EDIT]
A shared hosting service is not very suitable for the app created with the advanced project template.
I have just installed yii in local in my pc… i have created the web app in my localhost… and now i nedd to publish the app online on my hosting. example: www.mywebapp.it
I have installed online the advanced template with Production mode and i have copied the frontend and backend directory from localhost to online folder.
As I said in the first reply, the installation process of your app to the production web server depends heavily on the environment of your hosting server. So, there’s no detailed guide for every specific hosting service.
But if your server is a VPS or a standalone server … I mean, not a shared hosting server … and after you have setup it to run apache (or nginx), php and db server like mysql or postgres, then the rest of the process is almost the same as you do in the localhost.
If your server is a shared hosting server, then you may want to read this: