Well, assuming you've already uploaded them, the next step is rather easy. Above the row of smileys, the second button from the left, is the Insert Image button. When you press that button, the forum software automatically inserts the BBCode needed for the image to show up.
But before you do anything with that, you need the image's web address. Simply open it up in the gallery, right click on the image and select "Copy Image Location." Then you come here, put your cursor where you want the image to appear, and paste the address in. Once you've done that, all you need to do is use your mouse to highlight the entire address and click the Insert Image button.
It's always a good idea to preview posts before posting them to make sure your image is where you want it.
