Hey Tat. Just a word of caution. When you use an attachment it will be part of your attachments forever and can't be deleted. You're only allowed 20 I think so it may be more beneficial to copy and paste the URL like this:
Right click on the image.
Copy image URL.
Then click on the little picture in the quick reply box (second one from left. Looks like a mountain with the sun)
Paste the url there and click "ok"