Well Jyoti, it depends on your skill level as a whole. To effectively use graphic design to design a website, you need to know how to use graphic design applications such as MS Photoshop or the free Gimp. Both of these allow you to create great looking graphics which you can use on your website or template. A point to note though is that graphic design is artistic in nature and you must have a natural born talent to produce the great looking graphics you see on some sites. If you are like me, who hasn't got an eye for design, hire someone to do it for you or purchase a ready made template with the graphics you would like.
Hope I have answered your question appropiately :)