You can change the font size and screen zoom in Settings》Display and you'd bee able to see some more content.
If you mean the Pop Up window function: Go into the task manager and tap on the app icon. Now you'll see the option to open the app in a pop up window.
Alternatively, if you mean the app icon size on your home screen: Tap and hold a page of your homescreen》Select "Settings"》Tap on "Home screen Grid"》Select your desired option
Optionally you can download GoodLock with the Module HomeUp from Galaxy Store and get some more customization options.