GNOME is a powerful desktop environment for Linux/BSD/Unix-like operating systems, but by default lots of useful features are hidden. The good news is there’s a tool called GNOME Tweaks that you can use to manage your GNOME instance and do anything from configure extensions, to change your icon pack and cursor.
To install GNOME Tweaks you can either run this command in Terminal:
sudo apt install gnome-tweaks
Alternatively you can launch the Ubuntu Software application and search for GNOME Tweaks and install from there by finding GNOME Tweaks in the store and clicking Install.