In almost every case, you spend years flying smaller airplanes, in general aviation and regional airlines, before you get hired at a larger airline.
You start as a FO, and stay there until people senior to you retire (or quit) and opening becomes available. The larger airplanes usually go to the most senior people...you will have grey hair and probably grandkids before you get in a 747 at a major airline.
A few forieg airlines hire CA's off the street, but these are always people who already have CA experience in that airplane.
Getting simulator training or a type rating in a certain airplane will almost never get you a job in that airplane. You get the job first, based on your experience level, and then you get training on the specific airplane you will fly (usually at the company's expense).