Now this one should be in the help forum, Baloki

To put images in your sig, go to "User CP" (the link is up there by all the FAQ, Members List etc links) then on the left sidebar, Edit Signature.

Use {img}http://imageurl.com{/img} replacing in the image url, and also replacing the } and { tags with ] and [ ones.

To attach pictures to posts, you can also use the img tags or at the bottom of your post space, there is "Additional Options" and under that there is "Manage Attatchments"