Easy.
Get the image URL and use the image button to get the (img) tags on each side of the url.
You get something like this:
Next - put 'width=300' or something inside the first tag - after the 'img' and put a space in before the end bracket:
Use the Preview button to see if you like the size. Keep changing the width until you like how it looks.
Hey Waldo!! You paying attention???