How do you lock the trunk on a 2015 200?

Review the owner's manual. On many vehicles if you have the key fob near the car the trunk will open.

go to your local hardware store and by a latch and padlock, this will solve your malfunctioning tailgate

I locked my keys in my new Chrysler 200 and the key fob is cover by some paper and i can't get into with a metal hanger how can i get my car unlocked?

None of the above answers tell me why trunk access is available to anyone @ anytime; even if key fob is no where near the car.

Which latch button are you referring to? Either your car was left unlocked and they can open your truck via button by interior dimming. Or they got ahold of your spare fob....

How do you disassembly the trunk push button On 2015Chrysler 200