linux library installation

I have recently switched from XP to Linux (Zorin, a Debian distro) and spent may hours trying to install a library. I could not find a straightforward way on the internet, not even on this forum. Here is how I managed it but I would like to know a better way.

When I download the zipped library file, say call it XXX.zip, it lands up in ~/Downloads
In terminal:
unzip XXX.zip (and it unzips in /Downloads/XXX and makes its own sub dir)

My arduino library files are located in /usr/share/arduino/libraries (root only accessable)
The struggle was to find the commands to make a sub dir XXX and copy the unzipped XXX files in there:

cd /user/share/arduino/libraries
sudo mkdir XXX (make a sub dir XXX in /libraries)

cd /Downloads/XXX ( go back to the unzipped folder)
sudo cp -R * /usr/share/arduino/libraries/XXX (copy the lot including sub dirs)

cd /user/share/arduino/libraries/XXX
ls (and check if its all there...)

I can now import the library in a sketch and it compiles ok.

The other problem is that I have no permissions to access the XXX example folder (all the other example folders under the library are accessable. How can I change the directory permission?

Thanks
Hans