The splice manipulator creates manipulated mobs using the traits you provide.
Use:[]
Place an empity egg in the middle slot (empty eggs are created on the Embryo Synthesiser). Place traits all around it (if you're not sure about the exact position click on the help button (question mark) on the top left corner).
Provide the machine with power and after a while you'll get a spawn egg. Right-Click with it to spawn a baby splice with those traits.