Sorry that the picture-posting process is giving you difficulty.
In a certain way, if you just blindly follow instructions it will work, despite the fact that it looks like it is not working.
Start a posting or a reply to this one here. Next "Preview" to get the full options available.
Under the text box, there's a + button and it says "Attachments and other options" beside it.
Click that button.
Next choose the file from your hard drive. When you select the file, and the dialog goes away, the name of the file is now in the Attach: box.
Beside that box is a pull-down list. Select one of the two things. DO NOT SKIP THIS STEP.
If you selected "inline" then a little line of code suddenly appears in your message. Leave it where it is and POST.
