If you wish to install packages in Zorin OS by downloading them off websites please use the following guide:
1. Download the package(s) from a web site. You can download free packages from recommended sites such as GetDeb (for applications) or PlayDeb (for games). Commercial, paid-for applications and games can be acquired from LinApp.
2. If the package has a .deb file extension, locate it and open it. Then click install. If your package is not a .deb, please read on.
3. Extract the package by right clicking and pressing "Extract Here".
4. Enter the folder and open a Readme file (if there is one). There should be a section with installation instructions, please follow these. If the file doesn't have installation instructions there should normally be website link that (hopefully) includes the instructions.
5. If none of the above instructions match your situation try using some popular commands in the Terminal. You first have to locate the file using commands: cd (the file location). Example: cd Downloads/[insert-program-name-here]
6. After you have located the folder try using commands like the following:
"sudo make install" or
If none of these instructions work for you please check the package site for further details on installation or post a comment on the package maintainer's website.