If you have a PC you can use "Paint". The program is part of Windows operating system. Right click on your picture, choose" Open with" and then "Paint" and it will open in the program. Look for resize. If you need further help let me know.
I downloaded a free program called faststone. It is easy to use and It allows you to resize photos and numerous other things too. You can also size several photos at once and specify where you want them all saved too. There are tutorials online that show you step by step how to do it. Once you have resized your photos if they are still not small enough you can resize again