Timthumb does not work (Magazeen theme)

I downloaded Magazeen theme and edited my website http://www.jryp.net

But the timthumb image never worked, it only shows the title of article rather than resized image.

So I searched on Google, and found this article to use smart image resizer to replace timthumb

When I correctly replace all the required file and code, it’s still not working. Thus I checked the replies to this post and I noticed that I have to install gd library.

I have no clue how to install although I searched on google, and I am not sure whether the timthumb doesnt work is due to this GD library.

Anybody help please, really really appreciated