Espionage Headquarters grants you the ability to spy on other countries or protect yourself from being spied on. It is located on the vertical left of your screen.
Select the province you want to put the spy on, and decide between Intelligence, Economic Sabotage and Military sabotage spies. Recruiting a new spy costs 15.000$.
Select the province you want to protect and assign Counter Espionage spies.
Spies on a mission will perform their mission and get paid once a day, but can also get caught. There is no limit on how many spies you can put on a province! The different kinds of spies serve different interests:
Counter Espionage Spies counter and reveal enemy spy activity on your territory. Intelligence Spies gather information about the enemy's diplomatic relations and economical activities. Economic Sabotage Spies damage the morale in the province they're put in, as well as destroy resource production. Military Sabotage Spies try to interfere with the enemy's military plans and infrastructure.