Your files are too big, they have to be under 100kb.
If you have Microsoft Office on your computer you can right click on the picture and choose Open With, Microsoft office picture manager.
Click the edit pictures button and resize it.
Here is a how to article
Watch this: Use Picture Manager to resize pictures - Support - Office.com
Or you can go online to a bunch of different sites, here is one.
Web Resizer - Making Photos Faster - Optimize pictures for websites and email