if you're trying to resize an image for your avatar, use a program like paint or something online
to resize images on the web to display in a post, use [img width=# height=#]image link[/img]
the size of an avatar is 75x75, so [img width=75 height=75]https://s-media-cache-ak0.pinimg.com/564x/94/25/95/94259568884cfb1b6e0c00cf12b427ea.jpg[/img] becomes
the normal size of the image is