Hello Chinese Jack!
My diagram was not clear, what I meant is that the data pins are up to you to decide what is going to be sent.
Imagine that your remote control has 4 commands. So each of your HT12E data pins are going to signalize each command. You will connect each pin to each button in your remote control, for instance.
The data pins are not a priori meant to be connected to an Arduino, but to your remote control instead.