I can't help you with the owner question, but I can with posting a picture from your desktop.
After you are logged in, there is a row of symbols and icons above your reply window. If you hover your pointer over these, it will give you info on what it is. The button just to the left of the smiley is insert image. When you click on it a small window pops up with drop image or click here. If you are familiar with how to drag and drop, just drag it from your desktop over the box. If not, when you press click here, a window will pop up showing your computer files where you select your desktop and then the image you want, press open at the bottom of your window and it should populate your post. You can also simply press the "Attach Files" button on the lower left corner of the reply box and the same box will appear showing the files on your computer. just go to where you have the picture, (desktop) and select picture and press open at the bottom of the window.
To check you have what you want, press preview before you post.