Start by picking out a photo you wish to use for the front of your greeting card.
Open the photo you picked in Photoshop Elements Editor. If you're starting from the Organizer, right click on the photo and choose Full Edit.
In the top right corner of the Editor, click the purple CREATE Button.
In the CREATE panel, click "More Options >>" and then Greeting Card.
Keep page size at 5 inch x 7 inch or set this if you have something different there.
Choose a theme and layout for your card. I chose "Hollyberries" for the theme and "One Portrait Vertical" for the layout.
Check the box "Auto-Fill with Project Bin Photos" and then click Done.
Photoshop Elements with generate the layout and place your photo in the card.
Notes for Photoshop Elements 5 Users:
In Photoshop Elements 5, start from the Organizer and chose "Create" from the shortcut bar, then choose the greeting card option. The New Greeting Card dialog will open. The settings will be the same as shown here, but some of the theme choices will be different.