Hello Emmy! Do you use a computer programme linked to your digital camera to download images?
For my (Lumix) camera, there was a programme called Photofun Studio, and I have a second photo library on my laptop called Picassa.
First, highlight the image to want to Resize, the look for "Tools" in the Menu.
In both of these programmes, I can go into "Tools" on the top Menu, and there you should find (??!) a "Resize" tab.
If you can do this, have a look, and play with it to see how you can change the Digital Image size of the Image File.
Often, to send an image by email requires a smaller sizing, less than 1MB, and I usually try to resize my photo images to 1024 x 768, which as a rule of thumb gives a file of about 700KB (0.7MB)
Have a play with an image which you can afford to lose if it goes wrong, and I'm sure that you'll be telling others how to Resize before long!
Let me know if you can manage the above, and if not, I'll try to help as much as I can, unless there is a budding Microsoft Person out there somewhere!
Good luck and best wishes,