This mission can be picked up at Franklin's house. Get in the car with Lamar and Stretch, then head on over to the Ammunation store. Go inside and buy a Pump Shotgun, as well as the Flashlight attachment. Once you buy it, head back out and into the car again.
Drive to the next waypoint, which is a warehouse for a drug deal. Head inside and up the stairs, only to find out it was a setup by the Ballas. For now, you will need to go from room to room, killing all of the enemies that come across your path. Since you bought a nice shotgun before, that should be more than enough, as you will likely pick up an Assault Rifle and Micro SMG from the dead enemies.
Not far from the exit, you'll get a three-star wanted level. When you leave the warehouse, the first thing you'll see is a helicopter, so shoot the chopper itself or the gunner to get the heat off of you. Follow Lamar and Stretch up the ladder, then keep following them as you run from the cops.
When you jump over the wall and land in the street below, hold up the incoming car to get the driver out. Jack the car and then you will now need to lose the cops. It's best to keep turning whenever you get to the point where the stars are flashing, as the cops will end up spotting you again. If you can find a hiding spot, that's even better. Once you lose the cops, drive back to Franklin's house to finish the mission.