We strongly advise against editing files directly on the file system due to a strong possibility of crashing the store. If you need to change theme or plugin files, use the code editors inside WordPress since they have code checks that will prevent you from adding changes that can crash the store.
Theme editor is available under Appearance > Theme Editor.
Please note the warning - all changes will be overwritten with a theme update. It's highly recommended you create and edit the child theme instead.
Plugin editor is available under Plugins > Plugin Editor.
Please note the warning - all changes will be overwritten with a plugin update. It's highly recommended you do not change plugin files unless you know what you're doing.