Here is a great site you can use without either downloading and installing software or having to upload your large images to do the editing.
Go right to the site and it opens like it was installed on your computer. Locate the images on your computer, then click Image > Image Size. When you have it the size you want, File > Save and give it a name and location. Easy as that.
It also lets you do many editing tricks like cropping, rotating, and even adding wording right on the pictures. You can even grab a picture off Facebook or anywhere else on the Web, change it, and then save it on your computer or even post it to your Facebook page without ever saving it on your computer.
Here is a link to a good video on using this site and also how to use Paint to resize.