Game of Thrones: When exactly to use the Valyrian Steel Blade when playing with Tides of Battle?
"Now" means during the step being discussed by that explanation: the Valyrian Steel Blade step.

The Valyrian Steel Blade step is the fourth out of six parts in combat, as listed in the rules.

It occurs after the Choose and Reveal House Cards step, which is third out of six.

The rulebook and the FAQ/errata both imply that the Blade happens after the TOB cards. Either the TOB is "part of" the House Cards step, or the Blade follows the choice and revelation of TOB cards.

Nevertheless, you will have seen your opponent's Tide of Battle card (and thus know the pending result of combat) before you decide whether to use the Blade.