I found your other thread where your RemotePi board is visible. Looking at your pictures in that thread the RemotePi you have doesn’t seem to be the model shown in post #223, but this model with external IR and LED.
This variant of the RemotePi board comes with external IR receiver and LED cable assembly which appears to be connected on the picture you posted. So you should already be ready to go hardware wise - at least if you have done the mentioned hardware modification to the RemotePi board.
On the software side you would only have to
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install the remotePi plugin, enable “Use GPIO port 17 for IR receiver” and reboot.
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install the IR Controller plugin and choose your remote control.