Could you post a screenshot of the top part of your browser, a view such as this one -
You can use Command-Option-4 to get a crosshair, then drag that across the area you want to capture. When you let go a screensot of just that area will be dropped onto the desktop.
Then use the camera icon in the reply text enty box's toolbar in these discussions -
when you click that icon, you'll be asked to choose a file (meaning the screenshot image file); navigate to it on your desktop, choose it, then click the insert image button.