There is no how-to. You would have to do it on your own. But most of them are in /var/opt/rcware /tftpboot/ and you will also need /www/ and of course the init scripts /etc/init.d/ - scripts and nginx and maybe some libraries…
By the way what is the purpose of this? We worked hard on making the system as much read-only as possible in order to keep your sd card safe... It might be easier to install your packages on the distribution that we created.
Thank You for the response, I was charting out how I was going to setup the controls for the system and while lining it up the weather came to mind and had to ask. Currently I am just getting the system up and going so automatic control will come at a later date, at that point I will dig into it.
The time of how often your program is evaluated depends on the complexity of your program and of course on the performance of the HW. I have tested that a simple program like your on RPi 2 B is evaluated every 30ms.
You can do a small speedup by changing the sleep time between every loop - in order to do that you need to switch to your main Profile and then on the PLC change the sleep time parameter (default is 50%).