Quite simple really, select Career from the main menu and Career again, here you will be able to choose a "medium" length season - 12 races.
You CAN retire from every qualifying and race and still get this, however you might as well put it on easy and win all the races until you get this achievement
My advice would be to race for Mercedes as Hamilton rarely seems to come in anywhere but second (if you are first) so by the time you win the Driver's Championship you should have already won the Constructor's title too and got this achievement if you hadn't already
Once you have both then you can retire from every session until the end of the season for the achievement to pop
