What do you mean by "where"? An orbiting manned space capsule fires "retro" rockets to slow it down and that brings it out of orbit. From memory it had to be going at a speed within a "window" too fast and it would "bounce" off the atmosphere back into space, too slow and it would plunge in too fast and burn up. They always used to show a diagram on TV of it skimming up and down 2 or 3 times on the upper atmosphere before curving down and deploying drogue shuts and then proper parachutes. The point where the retro rockets were fired was calculated by people who knew lots of "stuff". Considering the speeds involved it is amazing how close they got to the target landing point with Apollo though I believe at least one Soyuz capsule had the cosmonauts stranded out on the Steppes for hours.