Google doesn't supply printed manuals. The little articles on the website are clear, but there are many of them, linked to each other, so it can be hard to figure out what you want to read (or what you've already read).
"Beginner's Guide": https://support.google.com/googlenest/answer/9248184?hl=en
Scroll down to the "Nest Thermostat E and Nest Learning Thermostat" section (if you're sure that's the model you have) and read the articles on controlling the thermostat and so on.
Note that there's an article titled, "If you moved into a home with a Nest thermostat already installed" that you may need to read first.
Finally, not to sound too negative, but if you're truly not tech savvy you may be happier installing a more basic thermostat of a type you're already familiar with. The Nest is a programmable thermostat with various "smart" features overlaid on the basic operation. It may be too much.
