Go to the site that has the picture or video you want to use. To find the embed code choose SHARE. You will be given a choice to post to various places or get the link to copy and an embed code (on Flickr it was called HTML or BBedit code). Copy the embed code.
Now you can save, publish or preview to see that the picture or video that you wanted to show is now on your webpage.
The reason to use embed code is that the picture STAYS on the site where it was originally and you just put in a pointer to that place. When someone looks at your page the computer automatically gets the picture or video from the other place and puts it on your page.
Tomorrow we are back to Facebook!