A very ambitious project indeed
A known fact in PKDM cars is cost cutting which includes missing wiring for accessories or features like this.
As mentioned in the product description you need a 10-Pin spiral cable and not a 5-Pin spiral cable.
Have you checked what KIA motors has provided. Maybe the PKDM Picanto has a 5-Pin Spiral Cable and you might need a spiral cable as well.
Additionally you will have to check how many wires are coming out of the backside of the spiral cable.
1 Should be horn and and you can check the wires for the existing buttons, how many are they. Lets say 3
So total 4
Which means if the backside of the spiral cable has more than 4 cables coming out then you may have pre-installed wiring to the ECU otherwise that will have to be done as well.
Lastly most of the time PKDM models have speedometer/instrument clusters which either dont have the cruise indication LED or sometimes the whole circuitry on the board is missing so you will have to check this as well otherwise instrument cluster/speedometer will have to be changed as well.
So do all this research before ordering any parts.