Reshiram learns Fusion Flare and Zekrom learns Fusion Bolt. If you made one of them forget those moves, go to Mistralton City and go to the house next to the Pokemon Center and one of them will make your Pokemon learn that move in exchange of a Heart Scale.
get the TM and teach it to it
Milotic, Empoleon or Vaporeon.
Inside Drayden's house, Iris will teach you Draco Meteor. In white, Drayden will teach you because you will be fighting iris in the gym.
Teach it to a Pokemon, enter the Pokemon screen, chose the Pokemon that knows fly and select where you want to fly to.
Teach one of your pokemon 'flash' using a TM/HM
Zekrom or Zoroark are the best in Pokémon White.Another OpinionZekrom and Thundurus are the best Pokémon in Pokémon White.Another OpinionZekrom and Victini are the best Pokémon especially the event Victini due to its event moves of Fusion Flare and Fusion Bolt.
get the TM and teach it to it
blue flare is a move exclusive to reshiram at lvl 100. emboar can't learn it.
In Pokémon Black and Pokémon White, the moves that Reshiram is capable of learning would include ones such as Dragon Rage, Fire Fang, Ancientpower, Imprison, Slash, Extrasensory, Slash, Dragonbreath, Flamethrower, Hyper Voice, Fire Blast, Fire Blast, Outrage, Crunch as well as its signature attacks of Fusion Flare and Blue Flare.
All you do is get one, then teach it to a Pokemon that is able to learn it.
Milotic, Empoleon or Vaporeon.
Inside Drayden's house, Iris will teach you Draco Meteor. In white, Drayden will teach you because you will be fighting iris in the gym.
Get it to full happiness then go to Drayden's House. He'll teach it to you.
The last move Emboar learns is at level 62 which is flare blitz.
In Driftveil City, you can fight a "heartbreaker" biker. It depends on the version, in Black, he'll teach you about Rotation Battles; in White, he'll teach you about triple battles.
Teach it to a Pokemon, enter the Pokemon screen, chose the Pokemon that knows fly and select where you want to fly to.
Teach one of your pokemon 'flash' using a TM/HM