Answer
In practice that means learning to navigate a 5250 session or an emulator like IBM i Access Client Solutions, understanding what a library list is and why it controls which version of a program or file actually runs, and getting comfortable with basic commands like WRKACTJOB and WRKSYSSTS to see what the system is doing. It also means learning the shape of the roles around you: who has security officer authority, who maintains programs, who manages the console and job queues day to day, and what each of those roles is allowed to touch.
Once that foundation is in place, a beginner benefits far more from following one transaction, such as an order entering the system and moving through to inventory and invoicing, than from reading a general overview of IBM i architecture. That single-thread approach exposes object authority, job logs, and message queues in context, which makes the underlying concepts stick. Sandbox environments and community-run partitions are useful here because mistakes are cheap and reversible, letting a newcomer break something safely before they ever touch a production library.