For this, you need to finish the campaign
When you first enter career mode, you'll be given the choice between "Unique Stories" or "Daily Routine". Unique stories tries to give you a nice mix of new calls, and only requires you to finish these with a positive reputation. Daily Routine more simulates the life of a dispatcher. You may get exciting calls here and there, but also a lot of mundane calls. This option takes much longer as you have to cumulate a number of reputation points in each city before you can move on.
The cities are as follows:
Kapolie
Albuquerque
Chicago
San Fransisco
New York
Washington
Once you completed the requirements to pass each city, the achievement will be yours