This page of the Spider-Man Miles Morales guide describes the main questline mission - Someone Left The Lights On.... While searching the Phin family store, you will practice your newly acquired camouflage skills.
Rewards: 4500 XP
When you get to the designated location, jump through the window of the roof tower. Inside, you can take some time to look around the abandoned store. Scan the rooms to find interesting items such as guitars, a framed dollar or a backpack. In another room you will find Phin's ID card, a syringe and a list of Nuform programmers.
There will be a brick wall near the desk. Hit it with a Venom Punch to get to the secret room. Phin's mask is on the table. Go to the computer and play the video.
You will be attacked by members of the Underground. Follow the on-screen instructions, turn on the camouflage and jump onto the nearby building. Remember that invisibility is only temporary. You can now get rid of your enemies quietly, one by one or in open combat.
Watch out for more snipers appearing nearby. You will lose the camouflage quickly when packing punches. You will remain invisible when you sneak up slowly to the enemy and attack them from behind. Return to the computer to complete the mission.