You can’t add attachments to a post, but you can include references to files on a server. So if you can upload your files somewhere, you can include a link to them in the post.
You can also embed an image into a post, but again it’s just a reference to an image file on a server somewhere else. For instance, if you have found an image of an explosion that you want to show people, you can embed it here:

To do this, copy the image address, then click the little camera icon above (between the “U” and “L” icons), then paste the image address in.
Alan.
wondertouch