To get out of the camera push this button on the front of the phone near the bottom.
See the small version of that big circle with a square in it at the bottom of the phone? Any time you are in something and you want to get back to the "home" screen where you see all your apps, touch that home button
To make and receive calls all you care about is the button with the phone receiver on it.
To make a call...
How to answer phone calls... If the phone is locked, just pull the little green and white phone button to the right to answer, or push the power button to ignore it.
If the phone is already open, tap the green phone button. To hang up or ignore touch the red button.
I hope that answers it all!