The second advent candle represents Preparation–to get ready.

John the Baptist prepared the way for Jesus 2000 years ago:

As is written in the book of the words of Isaiah the prophet:
“A voice of one calling in the desert,
‘Prepare the way for the Lord,
make straight paths for him.
Every valley shall be filled in,
every mountain and hill made low.
The crooked roads shall become straight,
the rough ways smooth.
And all mankind will see God’s salvation.’ ” (Luke 3:4-6)

Similarly, it is good to prepare ourselves now for the day when Jesus returns to the earth. “Therefore, prepare your minds for action; be self-controlled; set your hope fully on the grace to be given you when Jesus Christ is revealed.” (1 Peter 1:13)