Question

whenever we lit up a candle why does it always points upwards?

Answer 1

A candle flame always points upwards because  the flame is extremely hot and thus  less dense than air .

Answer 2

A candle flame keeps pointing up because it heats the surrounding air, creating streaming currents around itself. Warmer air is thinner and lighter than cooler air, since gas molecules spread out when they gain energy. As the heated air near a flame expands, it also rises, since it's lighter than the air around it.