如何在Symfony2应用程序白页中显示错误

I am working in an web application and I got access to the files of the project. I am trying to run in local.

I've downloaded all the source code and the vendor libraries. Then I tried to run the project by the console.

It seems to work fine, but when I try to open the page in my browser it is just white.

I don't even know how to start looking for an error. How can we look for bugs or errors in this case?