We get asked this question regularly, so, here's how you can post photos on the Forum.
Method One (the easy way).
When you select "Reply", "New Topic", or "Quote" function, a text box will appear, where you type your post. At the bottom left of the text box you will see 3 image links labelled "Choose File".
Just click on one of these, browse for your image and click ok.
It's that easy.
NOTE: THIS OPTION DOES NOT WORK ON "SUBMIT QUICK REPLY"