How do you find libraries (C++) in Ubuntu?

Sorry, this is such a beginner question, but I’ve recently begun programming with C++ on Ubuntu 12.10 and I’ve installed a few libraries I need to work with, for example PCL and I can’t find them to add them to my project. I’m using Qt Creator as the IDE and qmake which comes with it.

For example, with PCL, I followed the instructions on their site:

sudo add-apt-repository ppa:v-launchpad-jochen-sprickerhof-de/pcl
sudo apt-get update
sudo apt-get install libpcl-all

And as no problems occurred I have to assume they are correctly installed.

Most of the tutorials dealing with adding external libraries I’ve found on the web assume you’re on Windows and know where you downloaded the library.

Since I don’t have experience with adding external libraries in C++, could someone please tell me in what file, if there is one, are libraries installed by default in Ubuntu?

What is the extension of these library files?

Is there a script/command which can help detect a library or all the libraries installed?

sudo updatedb
locate libpcl