First bike assembly – Brake levers

I should have got a mechanic to do it but it’s the night before my son’s birthday and here we are 😅: I’m on the final step and I can’t for the life of me work out how to thread the brake cables into the brake levers when there is so little ‘exposed’ cable to thread through. What am I missing? I can’t push down either case housing or or ‘pull out’ the cable any further.