For PC users: put your cursor over the picture, right click the mouse(a menu will appear) and then left click with the mouse on either "Save Image As" or "Save Picture As" (depending on your browser). Then choose where on your computer you would like to save the image, and what you would like to name it.
For Macintosh users: put your cursor over a picture, click and hold the mouse button down, and choose "save this Image as" from the pop-up window. Then choose where on your computer you would like to save the image, and what you would like to name it.