can someone edit this so I can use it?

http://imageshack.us/photo/my-images/651/smgun.png/

Just download gimp and dick the bar out from the left corner.

I used gimp to make it. I can't change the resolution to 800x600, and I don't know how to make the white transparent.

make a new image thats 800x600 with transperancy. Copy/paste that into it, center it, then amke it its own layer. Select the fuzzy tool and select the white, then erase. If it still makes it white, add an alpha channel then erase
http://docs.gimp.org/en/gimp-layer-alpha-add.html

I can't make it 800x600, only lets me make it 800x540.

lol wut? Im doing it now

ok, I got it to be transparent. how do I change the resolution?

You had to make a new image already, or go to layer > layer dimensions and make it 800x600
I made it longer for you too
http://i.imgur.com/X5Vx2.png

so i'd have to redo everything?

alright, I'm starting to get this now. I'm making another sight and I've resized the image and everything how to I get rid of the alpha channel thing around the resized part?

I think you're doing it wrong....go to file>new> and jsut make it 800x600., than paste in teh slab6 screeny then align it(make it its own layer), fuzzy select the grey, remove it with alpha channel on, duplicate the layer, add gaussian blur of 6 pixels to the top later, then use the eraser to remove the blur on the sight part of it.

here's what I'm doing. I open the image then go to image > scale image and resize it to 800x600. then I use fuzzy and delete the gray around the sight and it works.

well if you scaled it up on a layer that wasnt 800x600, a lot of it would be removed (if you had a full image). Thats when you do the layer boundry stuff