Hey there!
You could use an image editing software package (paint or paint.net in windows for example) to reduce the resolution and re-save the image.
Also, you could try to email or message them to yourself if on a mobile device. That should automatically reduce the size for sending in a message.
There are more ways, but one of those should work for you.
I've had best luck getting the size down to ~400kb, but I think the max size is ~700kb (roughly)
Hope it helps!
