I know this is absolutely pathetic due to the length of time that I've been here but it's been so long since I've done it that I've forgotten how to post a picture into a post?

I have a photo saved to my computer. How can I upload it when posting? I know there's the "Enter An Image" link (fourth from the left) above the reply box. But how can I either upload a picture from my computer or post one from the internet without having to post the website address?