i tried but it didnt work for me... help? XD

the size code you mention says it's a change font size code. An image , which is what you got, is not a font. This sCode will not work for what you want.

It used to be that Subeta would automatically resize images that were to big for forum signatures for you, but I've been seeing users post about getting Warnings. You will have to use your own image program or find an image hosting site on the internet to resize your image.