Restore default theme settings

I am very new to this.

I want to keep my information, but restore a clean version of twenty twelve. I delete it, re-install it, activate it and it is the same.

I saw on another question where someone was given the link to download the theme and then “extract” the theme.

I was able to download it, but I cannot figure out how to extract it.

Please be overly simplistic in explaining the process. Thanks in advance.