In Word Tools|Mailings|Envelopes and Labels|Labels|Options (or in the Label
Options dialog in the MailMerge process, if that is what you are using),
a. select the correct printer type
b. click New labels
c. fill in the dimensions of your label stationery. The details are usially
printed somewhere on the Avery packaging or on a piece of paper included in
the pack. Otherwise, you will need to measure them yourself.
d. Give the label a name, such as Avery 5567, and click OK
e. in the "Label information" dropdown, select "Other/Custom" and your
label should be listed.