You can do this with Photoshop. Open Photoshop and open the photos in it. Then in Photoshop, click on Image menu and select Image Size. Change the resolution to 72 to something lower. Close it and "Savs As" as JPEG. While saving, it will ask you to set the size and you will see the approximate file size as well. Choose the one that you need.
If you have only a few images, then you can use these online tools to reduce the size
You can also do this with iPhoto as well, but iPhoto will not give advanced options like Photoshop. In iPhoto, click on the photo or select the photos, click on File menu and select Export. You will see the resize options in Export screen.
Please let me know if that didn't work, so I will continue to help you until we fix the problem
Note : This is not my final answer. I strive to provide Excellent service or 5 star service. If you feel you've received anything less or if you are not satisfied or if my solutions didn't work, please don't rate me bad or poor as it will badly affect my job here. Instead, please let me know and I will try my best to help you until you are fully satisfied or the issue is resolved.