Ok. I've never known of an instance in the forums where the File Manager option for posting graphics has not been visible to select. I wonder if it's a restriction that's placed on new members for a short period of time?
Another way to post an image is to use an image hosting site on the web and then to post the image's link using the 'IMG' command. To do this, have a look at the graphic below...
...The URL for the image needs to be sandwiched using square brackets, forward slash and img exactly as shown in red below.