Thank you to everyone that helped me! I finally figured out how to do it by watching a simple youtube video! "https://www.youtube.com/watch?v=i1MwSK8Ww7A"
Like Jpkarlsen mentioned the package files aren't meant to be opened.
If the custom content files are .package files they can be copied to - C:\Users\Username\My Documents\Electronic Arts\The Sims 4\Mods
If they are in .zip or .rar format. They they need to be extracted into the same folder as above.
How To: Zip and unzip files - https://support.microsoft.com/en-us/help/14200/windows-compress-uncompress-zip-files
How do I extract files with WinRAR? - https://www.win-rar.com/faq.html#c1419
The .package files in my game aren't associated with anything. That's by default.
If you want to change the association of your .package files, here's an article that can help with that.
Change which programs Windows 7 uses by default - https://support.microsoft.com/en-us/help/18539/windows-7-change-default-programs
Ah okay, I think I might know why. Try logging into Origin and go to the Games Library and click on Sims 4 to play. This should create a new Sims 4 folder for you.
Once the game creates the Sims 4 folder, you should be able to find the Mods folder within it.
@e29960f376f5dcea You can change the file type association in Windows 7 control panel - default programs - associate a file type or protocol with a program.
