If you want to work specifically for a particular airline the best way is to ring them up and ask them boldly where their pilots come from. Tell them you want to become an eligible candidate for them and want to know the best way to get there. They should appreciate you getting in contact with them and will tell you what you need to know.
Another way is to ask the pilots of that airline how they got there.
But usually "wannabe" pilots don't target a specific airline, they'd be happy if they can fly for remunaration, regardless of the airline. At least during the first couple hundreds/thousands of hours. Then you'll be in a position of more or less "freely" choosing where you want to work.