Concisely Identify the Problem

It doesn't work. But what exactly doesn't work?

I want to connect to the internet using Bezeq's ADSL service. I know
that it requires launching a program (pptp) on my linux machine, which
connects with the ADSL modem and creates a VPN (Virtual Private
Network) . Then I somehow authenticate myself to the remote side and
get an IP address. 

In order to solve a problem, we need to first identify it. The best I
can do right now is 'it doesn't connect', which obviously, is not very
helpful, so I settle down for a few hours (which quickly turned into
days) to LEARN HOW ADSL WORKS.