If you're looking for free, go to stockcharts.com and choose "annotate" under the chart. When it comes up and you've done what you want to do, press Alt and PrintScrn on your keyboard. This will be sent to Paint.
Then open up Paint, select Edit/Paste, click Save under the File menu, and save it however you want: jpg, gif, etc. To upload it to ET, browse your Paint files until you find it, then upload it.