In your User CP, (top left) select Your Albums and then you can start up a album and download the photos from your computer. Once you have the pic's in your album. select a picture so it's big and copy the HTTP address, when you are in your thread or post select the Insert Image icon and then paste the link into it. Hey presto the pic comes up.
If you want to do more than one it is easier to open two forums so you can just flick between the two.
Hope this helps, took me ages to work it out, alot do it by links from photo bucket but I can't see these pic's on my work computer, if they are uploaded off your album I can.