You're right, the manual isn't very clear, but I would suspect that once in the learning mode (selected mode indicator flashing)...

• Press the Kuro button you want to learn to (mode indicator solid?).


• Press the button (the third party remote) you want to learn (hold for 2 seconds).


• Wait for 30 seconds, or until mode indicator starts flashing again.


• Repeat the process for subsequent buttons.