If you're using the onscreen navigation icons:

1. Open the first app.

2. Touch & hold .

   You'll see two screens. The bottom screen lists your recent apps. Also, is now .

3. In the bottom screen, select the second app to use.

If you're using the fingerprint sensor to navigate:

1. Open both apps so they appear in the list of recent apps.
2. Swipe right on the sensor to view recent apps.
3. Touch & hold the first app and drag it to the top of the screen.
4. In the bottom screen, select the second app to use.