You need some kind of photo editing software like PhotoShop, Elements, Paint Shop, etc. I've used all those over time. If you don't have any similar software, there are some freebies talked about here
- although I don't have any firsthand experience with any of them, somebody else here may be able to help point you in the right direction with one of these.
Another thing you can do is turn down the settings on your camera to make the pictures smaller when you shoot them.
Good luck - can't wait to see whatcha got to show us!