Anilph, current version of AVR studio is 6.0, so use the latest always. and this version comes with GCC AVR compiler (WinAVR) so you can start your program right away.
if you are using code vision avr, then to access portD 0 as output you have to set the data direction.
here is the sample code for CVAVR.
DDRD.0 = 1;
PORTD.0 = 1; //ON
PORTD.0 = 0; //OFF
~SwK.