Right-- this is very basic, very self-explanatory. Instead of using pull-down menus-- I usually go to Google Images, find what I want, then highlight everything in the browser, and press Command-C (for copy). When I get back to this website I do the rest of what Slayton says, using Command-V (for paste).
One thing we may want to add is that if you are inserting a pic in the middle of text (like between paragraphs) you will have to press the Return (Enter) key to separate the photo from the surrounding text or else it all runs together.
And an extra tip-- sometimes when I take something from Google Images, I crop it and resave it, then add it as new media on a page on one of my blogs. That becomes the address I copy and paste into my posts here at TCM City. Why do I do that? So that I can rename the picture under something I might remember more easily. And so I know a long time from now, my images will still be here, and there will be no hot-linking problems. It is all coming from my website, not some other website. I've done that with every photo in the 'It Happened on This Day' thread, because my intention is that the contents of that thread will survive a nuclear winter.
Can you tell I'm a control freak-- even when it comes to photos? LOL