How to get an apps source code for a reskin?

It's all in the title

Thanks in advance

https://clutch.co/app-developers/resources/how-to-reskin-your-app-six-steps#:~:text=A%20source%20code%20is%20the%20skeleton%20of%20your%20app.%20There%20are%20two%20ways%20of%20obtaining%20a%20source%20code%3A