Photoshop CS6 how to make area around sprite fit the sprite

[Laslod]

Hello! I'm trying to make a sprite to use in XNA and there comes alot of problems when there is a blank space around the sprite ( if i make it transparent it's not visible bu it's still there ) so I need to know how to make the area around the sprite fit the sprite.

Ex. I made a new file with 100x100 pixel but my sprite only occupies like 5x10 of the pixels in the middle. How do I make the the 100x100 go so that the rightest part of the sprite is the amount of pixels wide the image is, and the highest part of the sprite is the amount of pixels high the image is.

When I go to image>image size> and make it bigger or smaller, the sprite will also get bigger,smaller along with the image.

I tried using the marquee tool to get the height and width of my sprite in inches, and then going to image>canvas size> and make it the amount of height - width I got from the marquee tool but it still cuts some parts of the sprite.

EDIT: I found out how to do it, fixed all my problems with XNA finally. All I had to do was use the crop tool and drag the image to the size I wanted, then save it as png i'm good to go!