The image needs to be uploaded to some sort of site so there's a URL for it, then you'd need to put it in [noparse]
[/noparse] tags to look something like [noparse]
[/noparse]. Then you're pretty much done
Someone'll come along and help you with that if you don't understand it. For the time being, be patient, as a signature isn't everything on a forum.
As for your posting. Instead of posting twice in a row, use the edit button before that, and add to your post.