Can I use Candlelit Sanctum before Rek Sai Legend ability? | tcgmode

If i conquer the sanctum, can I use the battlefield conquer trigger to look at the top 2 cards (and recycle if I want to) before activating the Rek Sai legend ability, or do I have to announce I will be using Rek Sai before I use the battlefield effect? I'm 99% sure I can look, then activate R...