In the beginning, the Nazis tried two different ways:
forced emigration: In this element, the Nazi's tried to force other countries, such as USA, Britain, and others to take away the 'undesirables' that did not meet the requirements of the 'Aryan Race' (or master race). This led to a greatly increased amount in the population each country had, leading to them closing a door to immigration from Germany and Nazi territory.
refined neighborhoods: The next step the Nazi's took was extermination, and the first step was to isolate the Jews and undesirables in certain neighborhoods so that they were easier to take away to the concentration camps. This soon led to overcrowding and poor conditions, and was the first step to what is now known as the "Holocaust".
hope this helps!