Installing ppas

Before you can install your first ppa, you have to install python-software-properties so you can get add-apt-repository

apt-get install python-software-properties

Now you can try to add a ppa repository, e.g.

add-apt-repository ppa:gstreamer-developers/ppa
apt-get update
apt-get install gstreamer1.0*

And you may find the following very handy

apt-file search <something in some package>

as it will list the packages which may provide the operand.