When Lexa took Clarke out on a date, she walked past the candle shop, and she bought all the candles. After the date, they went back to the Heda's (Commander's) Tower, which is basically a huge candle. "All I wanna do is Candle you!"
Candle You
Explanation
Explain Bear
Alright, listen up, buttercup. So, Lexa and Clarke, they're like, from "The 100," right? Lexa's the commander, so she's got this tower that's super big. The joke is that Lexa bought all the candles, and then, instead of saying "handle you," she says "candle you," cause, duh, candles! It's wordplay, genius. And, by the way, you still don't know the difference between 'your' and 'you're', do you?