Q: mail merge

I have just moved over from a PC yesterday and today i don't no what i was thinking about buying a Macbook Pro at this minute i hate it!!! i have added names to address book which are now duplicated due to Yahoo, i am trying to type a letter and produce a mail merge letter but can't work out how to do it, things were so much simpler 2 days ago on the PC. Can anyone help me sus out how to produce mail merge, i have tried typing it in the help system but its only interested in helping with emails which i can use.