How do I get a picture in my signature?

I've seen people with pictures in their signature but I can't seem to apply my picture. If I press image it just comes up with '[img]' and nothing else. What do I do now? The picture is in my documents.

HAHAHAHAHAHAHAHAHAHAHAHAHHAHAHAHAHAHHAHA!!!!!!!!!!!!!!!!!
idk wut 2 tell ya dude
i had som1 make mines xD

u can use photobucket to host ur image and copy paste the image code to ur siggy....

Go to imageshack and host it, copy the direct URL to your image(should be last option in the page that comes after you upload).
Then go to edit signature and write the following without any spaces or new rows:

Imageshack URL : www.imageshack.us

And tada :]!!!

Final result example:
[x] Flame a person with no life
[x] Get 25 posts
[x] Get 50 posts
[x] Get 100 posts
[ ] Get 300 posts
[x] Get a zakum helm
[x] Scroll my own items untill they're godly.
[x] Rebirth to all magician evolves for all 4rd job AoE skills (Blizz,Genesis,etc..)
[x] Join a guild
[ ] Rebirth 10 times then solo zak