download any one of several free programs, eg I use
Image Resizer Powertoy clone.
Then select one or multiple photos using left click and big up arrow above Ctrl button, then right click and select "Resize Pictures"
which gives menu as below
and I use custom 690 width for this site which I think is the maximum. This allows easy resizing of multiple photos all at once and you can specify whether to replace originals or create copies (I create copies and keep originals)
Alternatively use an image hosting site like flickr and paste in links - cheers