Hi Martin
Apologies if I’m attempting to teach Grandma to suck eggs!
If you need to resize your pics down and use Windows this is a really useful utility…
https://download.cnet.com/Image-Resizer-for-Windows/3000-12511_4-75937402.html
and if you’re an Apple man there is this app..
https://itunes.apple.com/us/app/image-resizer/id437497330
Cheers
Paul Barnard