Looking at the keyboard shortcuts, there is a zoom in and out but when I hit the keys specified, nothing happens. Do I have to install an app for these to work?
Are you looking at the Super++ and Super+- keyboard shortcuts? These allow you to zoom the text size in a specific application. (On macOS, zooming in the browser, Terminal, etc. works similarly.)
If you're looking to scale all text on the screen, there's an option to do that in System Settings --> Universal Access.