There are 2 options for this:
1. Under the empty message field, click on the button “[color=#ff0000;]More Reply Options[/color]”
Then you will see the option: [color=#ff0000;]Attach Files[/color][color=#ff0000;] / Choose files[/color]
(If you have problem try our basic uploader )
Wait for your picture to be uploaded and you will see the thumb of the picture, after that you can use the
[color=#ff0000;]Add to Post| Delete[/color] options and you done!
2. [color=#ff0000;]Add the URL of the picture [/color] by using the small icon -> this is the easier way!