Candles go into the menorah from right to left, but they are lit from left to right. The newest night’s candle is always lit first, using the shamash.
Basic order
On night one, put a candle in the right‑most spot and light it with the shamash after the blessings.
On each later night, add one new candle to the left, so the candles are placed from right to left across the menorah.
Which direction to light
When lighting, start with the newest candle (the one furthest to the left that you added that night).
Then move the shamash from left to right, lighting each of the remaining candles in turn.
Quick rule to remember
Place candles right to left as you add nights.
Light candles left to right, always lighting the newest candle first with the shamash.
