I need to build an offline app for the desktop. Any help or better step by step instructions guide for Wappler would be awesome, please!

You can add a blank capacitor.js file. This file will be used for your plugin configurations and customisation.

Is there any reason why you have selected Framework7? It is a mobile framework. And for a new user can be quite complicated. There is also little support within the Community as not so many Users have implemented it. You would be far better off going with Bootstrap for now which is well documented, including routing with Bootstrap.