Head to the next waypoint on your map to locate the vehicle Mario told you about. Open your map and mark the garage so you can head there without trouble if you decide you want to keep any vehicles you find later in the game. Take the vehicle to the garage and park in the blue circle to save the vehicle in your newfound garage location.
Look in the nearby crate for a Beacon, then pick it up and select Rebel Drop from the menu. Request weapons, vehicles and other gear and artillery, then wait for delivery of the goods. At this point you need to complete the Liberation of Baia before you can continue. Once that’s done you receive a phone call from Sheldon. Make your way to the next marker on the map to being the next mission, A Terrible Reaction.