If you are using Pages '09 on your iMac, you can use the Avery Labels Templates.
Pages '09 can open up Microsoft Word files (filename.doc).
I downloaded a template for my Avery labels from the Avery web site as a Word Document and it opened okay in Pages.
The more you use the Pages and Numbers applications you will become more familiar with them.
If you can't get used to them and don't want to buy Microsoft Office for the Mac, you can download free NeoOffice.
This works and feels like Microsoft Office.
www.neooffice.org/
For all help with Pages, try the Apple Support:
http://www.apple.com/uk/support/pages/