Changes to the blog

I was browsing through the www, when I came across some blog templates. Some of them really look good. One of them is the one shown below. So I was thinking, hey why don't I change the outlook of my blog to make it more appealing. But there is one big problem. Being the bimbo me, I really have no idea how to put the template here. Remember that it took me so long before I actually realise how to put up youtube vids here. Well I think it'll be quite some time before I know how to do this template thingy. But if any of you do know how its done, please tell me. Thanks guys.