When you light your candle for the first time, always allow the wax to burn so that it melts across the entire surface and pools to the edges of the container. This will effectively assist in preventing tunnelling and help promote an even burn for the duration of the candle's life.
Pro tip: Light your Wood wick candle close to the wax (rather than the top of the wick) for best results. This helps your wood wick melt the wax close by and start the wicking/burning process.