Here's a how to I wrote for my forum.
I've seen quite a few people aren't sure of how to post pictures on the forum or how to use imageshack to host them, so here's a little tutorial to help out those who don't know.
First off, go to www.imageshack.us
and the first screen you come to should look like this:
Click on the browse button. This will take you into your My Pictures
folder on your PC. Find your way around and select the picture you want to host.
If you don't know how to resize pics on your PC, use this (optional) function. Tick the box and then select the size you want your large picture resized too. Choose the 640x480 as it is a large enough size for people to see the picture and detail, without slowing down dial-up users too much. Also it means not having to scroll the screen side to side when a large image is posted.
Click the Host it!
That will take you to the next screen after the picture is up loaded.'
It should look like this if your picture is bigger than about 200x200 pixels.
If you did host a larger picture because detail would have been lost if you shrunk it, don't worry, use the Thumbnail for forum (1)
that is circled in green. Copy the whole URL that is there and when you post on the forum it will come up as a thumnail image like the one circled in green. It shows the size of the image and when you click on the thumbnail in the post on the forum, it will open a new page with the full size image.
If the picture is under about 600x600 pixels, just use the Hotlink for forums (1)
circled in blue and copy the whole URL and paste it into your post.
While you can register on imageshack to keep track of all; your pictures, I found it didn't like remembering me when I went back, so I didn't worry too much.
If I want to put a picture up again that I have already posted, it's normally easier to just go back to imageshack and rehost it again.