How to update custom app built in Laravel?

[VinitGusai]

Hello Everyone. I currently new to custom app development and I had project where I need to update an app which was developed special for that store in Laravel. Now I want to update it's certain logic but I don't know how to get access to backend file. Please share a way in which I can add all the file into local update the code and upload it to the web.

Please share a way. Thank you.