If you start at night, and if the emergency light is off, your headlight should already be on (MSFS default feature).
The emergency light is directly connected to the battery bus so you can turn it on even with battery disconnected.
All other lights in the cabin are powered through the generator bus, but you can still manually close the gen bus to power the lights with the battery.
Procedure :
If not already, turn on emergency light (overhead panel, right side)
switch on the battery master (pilot panel, left side)
close the generator bus, "Gen Tie Man" > close (pilot panel, center/left)
turn on the lights (overhead panel, left side)
manually adjust each light knob
Then you can start your checklist. Beware that you will draw much more current from the battery and may have to wait the battery charge.