1. Run the right program.
2. Tell it to make the image.
3. Wait till it's ready.
1. Be sure that you know how to go back to the image if you need to.
2. It's even built in into Windows: http://www.pcworld.com/article/3011736/windows/how-to-create-an-image-backup-in-windows-10-and-restore-it-if-need-be.html
How is a system image created