What is the right way to connect synced op-1 and op-z to a daw like fruity loops *DUMB NOOB QUESTION ALERT*

hello there, new here… the other day i tried to connect my synced op-z and op-1 to fruity loop daw through line-in cables, which made my op-z’'s volume too low and barley heard it while the op-1 played… so my question is do i need more gear? thanks you!