Go to either
Tinypic,
Photobucket,
Imageshack or
P1cture.me. Upload it to either of the above sites (you might have to create an account first).
Now, after you upload the image file, you will (somewhere) be given a URL (direct link) to the image.
If it's Tinypic it will look like this:
h.ttp://i11.tinypic.com/111a1aa.jpg
Photobucket will look like this:
h.ttp://i111.photobucket.com/albums/o111/something/yourfile.jpg
Imageshack will look like this:
h.ttp://img11.imageshack.us/img11/1111/yourfile.jpg
P1cture.me will look liek this:
h.ttp://www.p1cture.it/images/11111111111111111111.jpg
All the 1s will be replaced with random numbers.
Now highlight the link that either of the sites has given you and Copy (Ctrl + C) it. Now Paste this (Ctrl + V) into the thread, and put the link in between two "tags": [IMG.] and [./IMG]. (Please remove the dots - also some of the sites will already put it in between [IMG.][./IMG] tags).
Now just Preview your thread to make sure it's turned out ok, and you're done!
