Once you have acquired Vito’s dossier, you’ll have to go to the district of River Row. Don’t start the mission yet; instead, wiretap all junction boxes and hunt down fuses and collectibles, save for the ones located in hostile territory.
Head to the marked location and you’ll find some hostiles in the area. You can go commando and attack them with guns blazing or whittle their numbers through stealth kills then finish the remaining ones with your guns. Take note of the gas canisters scattered in the place. You can target them during a firefight when there are enemies nearby. There are also two medicine cabinets in the immediate area if you need them.
After clearing the area, head to the italian restaurant. There's a Vargas painting behind the counter to be picked up here. You'll hear Vito screaming and cursing from behind the freezer so head there and break open the door to rescue him. A cutscene will trigger and now you’ll have Vito as an asset. He’ll tell you to flush out Grecco, you have to take out his rackets. This district's rackets “Union Extortion” and “Contraband” will become available.
Partnering with Vito gives you access to the Consigliere associate who can pick up and store your cash instead of you manually stashing them in your safe. Furthermore, once upgraded, the Consigliere can also pick up your kickbacks for you, saving you a lot of time and effort compared to collecting them manually from each of your underbosses every single time.