If he is asking what I think he is asking, given he says hes not that savvy with programs and theres no instructions I have seen - take the .rar file you get and extract it into the main Crusader Kings folder - either by putting the .rar file in the folder and extracting to "here" or by choosing the option to pick an extract path and browsing to find your CK exe file. You will need Winrar program to do this. Google it if you dont have it.
i.e. C:\Program Files\Paradox Interactive\Crusader Kings
The unzipped files will overwrite the original files, so just hit "Yes to all" when it asks you if its OK to overwrite the files. When you load up the game next time, it should display 2.1 in the top right corner of the main screen.
Most mods are installed in a similar fashion. But do check your install version before you do it - installing a DV patch over a vanilla CK install would probably be bad. Though recoverable by simply reinstalling.