There are two methods to add a photo/image to a post.
The first method is to upload the image to a web server or photo sharing website and reference the photo in the post body using the insert/edit image button. Using this method you can put as many photos in the post as you want to.
The second method is to place a check mark in the "Attach file(s):" box when you create a new post. When you click "OK", it will display a box that will allow you to upload Attachements. When you have uploaded all the attachments, click the back button and the post will be posted.