Consider that RPi is just another computer.
You don't communicate with RPi at all, you only use it to load your finished application and run it from there.
You need to use the Base Package on a Windows based computer, create your application and, while creating it, can only test it with the direct connection to your PLC. Once you know it works, that is when you load it to the RPi and connect your PLC to the RPi as well.