Like any other program, start at the beginning.
Let's begin.
1 Write down your scope of work, what is it that you need.
2. Write a sequence of events in general terms.
3. Review your notes.
4. Rewrite your sequence and this time add sensors, motors.
5. Review your notes.
6. Write down your I/o.
7. Rewrite your sequence and this time add the sensors and motors.
In this step, you are the operator and also the plc looking for the I/o to be made.
this is the starting point for all projects.