Enter all the details of your contacts into AddressBook. Be consistent as to which address is going to be your printing address (work or home). Chances are that you will want these people in your AddressBook anyway.
Create a Group & name it Christmas Card List (or anything you like)
Drag those people (from the All group list) on your Xmas card list into that group. That adds them to that group.
Highlight the group.
Select Print from the File menu.
Print style is 'Envelopes', select which address (work, home, other) you are going to use for you and addressees, etc

If you only want to print one label at a time I suggest you download Ambrosia's EasyEnvelopes widget. It is the best printing application out there for printing single envelopes. Just set up your preferences (click on the "i" bottom right corner). When you want to print you just click on the stamp. It is brilliant.