Go to the PS4 home screen
Highlight the game you want to delete
Press the Options button on the controller
Select Delete
Confirm Delete
To remove saved data, go to Settings
Select Application Saved Data Management
Select Saved Data in System Storage
Select Delete
Choose the game
Select the save files you want to remove
Confirm Delete
To remove game data from an external drive, go to Settings
Select Storage
Select Extended Storage
Select Applications
Highlight the game
Press the Options button
Select Delete
Confirm Delete