how to install yum,gui,drivers

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http://unix.stackexchange.com – sir, im a student.im so new to linux.i dont know any thing about centos 6.3.x86_64 i had been installed centos 6.3 x86_64 recently.but during the installation i did not get trouble. after that the gui of os is not appearing.i had tried 'startx' command.but -bash error is appeared. will you please to help to get through.. 1.how to install gui after the installation been completed. 2.how to install yum in centos 6.3 x86_64 3.how to install hardware drivers in centos 6.3 x86_64 my laptop configuration is... lenovo - G570 processor--intel(R) core(TM) i5-2430M CPU @ 2.40GHZ 2.40GHZ memory( (HowTos)