The principle of PLC is basically the same. Novices can contact some simple ones, such as Mitsubishi FX series. First of all, you should read the programming manual of PLC. You need to know the internal resources of PLC, which you need when programming. The most important thing is that programming should be as simple and clear as possible. These are all experiences accumulated slowly in practical operation. I suggest you use a PLC to test directly, so that learning is more intuitive.