It is done using a special kind of bolt called an anchor bolt. These bolts are a 'J' shaped bolt which are inserted in the concrete just after it is poured. Enough of the threaded end of the bolt sticks out of the concrete so that it can go thorough and secure the sole plate of the framed walls using a washer and a nut.
I'll provide illustrations of the bolts in both of these final configurations in a follow-up post.