What does the journal record, and do I have to fill it in?
Nothing to fill in. Every fill on a live account or the simulator is captured on its own and netted into round trips — scale-ins averaged, flips split — each keeping the stop and target it was opened with, the exit reason, slippage against what you intended, and how far it went for and against you before it closed. Simulated trades are always labelled as simulated.
The journal opens from its tile in the Command Center. Past trades from another platform come in through CSV import, which accepts common broker-export shapes, refuses duplicate re-imports and keeps imported trades distinct from the fills the platform captured itself.