This section will hopefully show you exactly how to put images into a forum post.
Step 1 - navigate to the image you wish to put onto your post in the photo gallery then click it so that it shows on its own.
Step 2 - Right click the image and click properties then a properties box will appear and next to the section name address (url) highlight and copy the address (circled in red <--)
Step 3 - go to the forum and on the "Post a quick reply" click the button 3rd from right its supposed to look like a little window its the one to the left of the smiley face. (when you hover over it, it will say "insert image"
step 4 - once you have clicked that button it will show a little box <-- right click in the text field and paste the url that you got from the previous steps.
Step 5 - click ok and the image will appear in that chat box just scroll down to the end and type what you want.
Additionally - the images can look quite big but when its posted its not too bad but if you require you can re-size the image by clicking it and you will get drag boxes in the corners which you can drag until the image is the size you require.