If the postcards are the 2-up or 4-up type from Avery or the like, go to
Tools | Envelopes and Labels and choose the Labels tab. Click the Options...
button, select the appropriate brand, then scroll down to find the matching
stock number. OK out of the Options dialog and press the New Document button
to get a sheet of postcards. They're set up as a table, so be sure you have
table gridlines displayed (Table | Show Gridlines) so you can see the cell
boundaries.

--
Suzanne S. Barnhill
Microsoft MVP (Word)