It might be beneficial if you explain what you are doing and what problem(s) you are having and at what stage.

If you go to the File tab > Page Setup > Paper > Paper Size, scroll down the list to see your size and select it.
If it’s not there, use the Custom option to input your size.
Add content and assuming you have the 4 x 6 paper/card in the printer tray in the orientation reqd, you should be able to print out the card/document.
Note: The default margins may need to be changed for the small paper size.