The first thing you need to do is upload your pictures to a picture hosting website. I use Photobucket.
When you have your Photobucket account set up (Its free) go to the picture you want and hover the cursor over it. You will get a dropdown menu with 4 choices. The bottom choice is IMG. Click it and it will say "copied".
Now go to the post you are writing and place the cursor where you want the picture to be. Hold down the CTRL key and click the letter V. The picture will appear. You do not have to use the advanced posting option.
You can also watch a quick Youtube tutorial on posting a photo in the Forums using IMGUR.com. You don't have to open an account, just upload your photo. The procedure is essentially the same for using other photo hosting sites.