I wrote a series of Apex tutorials here on Reef2Reef:
www.reef2reef.com
However, before reading my tutorials, I highly recommend following Neptune's Getting Started Guides for the initial setup of the Apex and each of the modules:
This "Get Started" portal is here to make you successful with your new Neptune Systems product in as little time as possible. Select your product below and GET STARTED! Apex Apex EL Apex Classic Apex Classic Gold Apex Jr.
www.neptunesystems.com
Another great resource is Derrick Picker's Reef Automation channel on YouTube:
And then there's Neptune's Community Forums which contains over 10 years of Apex questions and answers:
This is the Neptune Systems Community where users get support, exchange ideas regarding the use of the Apex AquaController Aquarium monitoring and control systems.
forum.neptunesystems.com
Good luck!!!