Posting pictures

Please excuse me if this seems a futile question but I’ve searched to no avail.
I can’t seem to post pictures. I upload the pictures to the photo tray. It says ‘Drag and drop photos to post.’ Upon trying to ‘drag and drop’ there appears the captions ‘Sub post on,’ ‘thumbnail’ (in strikethrough), ‘delete’ ‘close’ and ‘se.’ If I attempt to ‘drag and drop’ there only appears a symbol meaning it’s impossible.
I would appreciate any comments.