Yeah there's lots of free options out there to host images and other files, no reason to host them on CP's servers, so no one has permissions to attach a file to a post.
__________________ Uncertainty is an uncomfortable position.
But certainty is an absurd one.
I've tried following those steps and the image doesn't show up but my imgur link does.
Does it take a while? First time image poster over here!
You need the actual image address with the .jpg, .gif, .png (etc) extension on it, not the link to the imgur.com page. The easiest way to get that is to right click on the image and "Copy image address". Then, put that inside the [img] tags.
__________________
Turn up the good, turn down the suck!