I need to install libconfig but I do not have access to root to be able to do apt-get install, how could I install it?
If you want a local installation, say in your home directory, you can use
apt-get (or the github link) to fetch the source and configure it to build locally, usually like this (change directory as needed)
apt-get source libconfig cd libconfig... ./configure --prefix=$HOME make make install
If you need a global installation, you'll need root or