Let’s try to give you a bit of clarity. The main purpose of the package manager is to take care of installing software into the right places.
Say, you want to install a certain app, e.g. the video editor shotcut.
You don’t go to
and download the package from there. Instead, you open your package manager (or even better: the Ubuntu software centre/store), search for “shotcut” and install it from there.
Alternatively, you can open a terminal and type sudo apt install shotcut.
Either way, you don’t need to bother about dependencies and where to install the stuff. It will also be automatically updated.
Now. If you really can’t find the app in the software centre, you might have to download the archive. You already managed to extract a tar archive, take a look at its content:
There is usually a README file or a text file with installation instructions. If you’re still at loss, name us the particular app, you’re trying to install, and some of us will probably try to guide you gently through the process. (no guarantee though, we do this when we’ve got spare time)