When in doubt about copyright, don’t use it. Screenshots are good but don’t crop so tightly that it looks like you are stealing the image. If possible, take your own photos or create illustrations or visualizations.
How to Search Google images for images that are free to use on your blog.
Click on “Settings” in the lower right corners.
Click on “advanced search”
Got to the very bottom and choose “Free to use or share”
If you plan to use the image for commercial purposes: For an ad, or as an image on a business or commercial website, you need to choose the “free to use commercially option”
If you want to change the image, you need to choose the “free to modify” option.