Before & After
Download an app called 'Snapseed' from apple store or android market. I guess it's free at the moment.
Open the photo that u want to edit
Choose 'Tune image'. There will be several things that u can change. Firstly, reduce the brightness to the number that u want.
Then, add Ambiance to ur photo to control the balance of the light.
Add contrast, to make ur white go lighter and ur black go darker.
Add saturation, to increase saturation or vibrancy of the colors in your photo
Lastly, adjust a little of your white balance to make it kinda warmy feel.
Here is the final photo. Pls enjoy ^^