Need some simple help with resizing an image to the proper dimensions

So I have this photo located here that I wanted to make as my avatar:
http://36.media.tumblr.com/3c61e043431da4d2f47e0e701a825f00/tumblr_n380lx8Y7Z1tucx3po1_500.png



I usually use www.picresize.com to change the size to 150x150 (the dimensions for a donor avatar). However, this image has a lot of empty useless space on the sides, so as you can see when I resized it and made it my avatar, it was a lot more compressed than it should be.

Since it's a transparent background I have no idea how to possibly snip the sides off so I can enlarge the image as much as possible and get the most use out of my avatar space. Can anyone help me out?

The solution might be extremely simple, but I'm inept when it comes to this kind of stuff

 

http://i.imgur.com/VQOJtlD.png

Here you go m8 I cut out a lot of the blank shit

 

lol no. you just cut out the blank parts, but now it's no longer transparent. that's the problem, I need the sides to be transparent. that picture now has a white background.

 

This should do the trick

 

Awesome it worked, thanks arc. This can be closed.