You need to do them one at a time. If you want to post two or more picture into a post, you just copy and paste the code that is given to you upload the image into the body of the text instead of the normal "optional image url" box. If you want the image centered, you need to first put [ center]-leaving out the space. I needed to put the space there so you could see it. Take a look at the top link to "formating" that will explain all the little code things.