There is an icon on your desktop to use in launching LibreOffice Manager. Before using it, open Synaptic > click Reload > click Mark all Upgrades > click Apply and again click Apply in the confirmation window.
LibreOffice Manager can be found in the menu as well >> Office > LibreOffice Manager.
Avoid installing from outside sources. You can break your system doing that. We provide a place for requesting apps not in our repos, the Package Suggest section. Be sure to read and follow the rules posted in that section when making a request.
If you need to run something as root, in the most usual cases, when you launch it, a login window will open first to ask for your root password. All of the common tools, like Synaptic and PCC do this. Everything that must be done as root can be done from your user environment. All of the tools for this you need are provided, either already installed or available through Synaptic.
You should never run as root. Especially never log in as root and connect to the internet. That is a big security risk!