You will need:
Step 1: Turn on TV and PS4
Step 2: Insert External Drive
There are 2 USB ports on the front of the PS4
Step 3: In the Main Menu, Go to "Settings"
Step 4: Click on "Application Saved Data Management"
Step 5: Select "Saved Data in System Storage"
Step 6: Select "Copy to USB Storage Device"
Step 7: Select Game to Copy
Step 8: Wait Until Transfer Is Complete
Repeat steps 4-8 for multiple games