How do I install apps from the terminal on Linux Mint Cinnamon?

`sudo` means “run this command with administrator-level privileges,” similar to running something as an administrator on Windows. Mint will ask for your normal login password; you will not see characters appear while typing it, which is normal. Only use `sudo` with commands you understand. If APT reports that a package operation was interrupted, run `sudo dpkg --configure -a`, then retry `sudo apt update` and the installation.

Flatpak is a convenient option for applications such as Spotify and Opera GX. You can install them through Mint's Software Manager, or from the terminal after Flatpak is enabled with commands like `flatpak search spotify` and `flatpak search opera`. Then install the exact result shown by the search, for example `flatpak install flathub com.spotify.Client` or the Opera GX application ID listed by the search. Using the Software Manager avoids having to remember those IDs.

On Mint, the usual tool is APT. First refresh the package list, then upgrade existing packages if you want: `sudo apt update` followed by `sudo apt upgrade`. To search for a package, use `apt search name`, and to install one from the Mint repositories, use `sudo apt install package-name`. Not every application is available through APT, so the Software Manager and Flatpak are often easier choices for desktop apps.

For a beginner, the Software Manager is perfectly fine and uses the same package sources behind the scenes. Search for the application there, and enable Flatpak results if necessary. It is generally safer than downloading random installers from websites, and it will handle updates along with the rest of your system.