Yay! And things sure have changed:
How to place a photo in a post:
If it's on your computer, you drag it into the image box (see below) after opening the dialogue box. If you want to
LINK* to an image, click on the link button and paste the URL into the box that opens. The symbol to LINK is the right hand symbol on the upper left of the box. (Looks like a tilted infinity sign.)
No need to resize, as the server will do that for you. Choose full size image, not thumbnail.
* Photos from many—even most—websites can be displayed by copying the image's URL, usually by Control-clicking onna Mac; or right-clicking on Windows, selecting the URL (often stated as "Copy Image Location" or similar words), then copy/paste that into the window.