A permission group is essentially a contact group from a gmail account and can be used to give a group of people access to a Google Doc or Site.
To start you need a Spreadsheet that has your contacts' information. We will start with a Google Spreadsheet here, as it is easy and free to use (An excel file would also work).
Locate the File menu in the upper left hand corner below the document name.
Cllick on file; download as; Comma Separated Values (.csv, current sheet)
Once the file has downloaded go to your gmail account.
Click on the RED Gmail button and load your contacts page.
The under the "more" menu heading, click on import and find your .csv file (it will probably be on the desktop or in the downloads folder). When located select "import" to import your file.
Once completed you can check for duplicates and rename your group from the "more" menu.