Firstly, enter the police vehicle. Follow the green semi-transparent blocks that show you the way to your destination. Reach the police station. When on-site, go behind the reception after the cutscene and rebuild the destroyed computer by holding the repair key (it consists of three parts).
Then follow Frank to the basement. You will be able to come back here to adjust some elements of the game after you unlock them: new disguises, vehicles and others. Go to the lower floor. Once there, destroy three crates from which you can then build (as previously with the computer) a wardrobe. You will also find similar objects in the world, in the form of police blocks, which you must destroy and rebuild. This is the way you unlock new character costumes. Now, change your clothes to a police kit.
Keep following Frank, in order to get the tablet and then connect it to the main computer on the ground floor of the police station. You can now call him at any time: he serves as a map, and will also help you in collecting secrets, by indicating their number in a given location in the upper right corner.
Follow Frank again, to the second floor. Activate the scanner in front of the chief’s office, in the location marked with several question marks. After doing that you will see footprints, which could not be seen otherwise. This method of solving some puzzles will be used quite frequently. Follow the footsteps, take the key from the cabinet and go back to the chief’s office. In order to wake him, go into his room, destroy the wardrobe and rebuild it into a radio.