The inside and outside can be printed onto different sides of a single sheet of paper or card.
First hide the inside layer and make the outside layers visible again so this can be printed first. If the paper you are using has a side for printing photos, ensure that you're printing onto this. Then flip the page around the horizontal axis and feed the paper back into the printer and hide the outside layers and make the inside layer visible. You can now print the inside to complete the card.
Tip: You may find it helps to print a test on scrap paper first.

