Set the box facedown.
Take a boxcutter, and slide the blade slightly out.
Find the seam at the bottom of the box, and gently cut through the plastic.
Using your fingers, peel the plastic wrapping back a little.
Tear the plastic off the box.
Slowly pull the top half of the box up.
Be careful! You don't wanna end up like this guy: youtu.be/7lhXOgJ8ahA
Make sure you keep the box and all its contents. If you sell the phone it'll have a slightly higher resale value. Enjoy your phone!