Anyone know how to do this?

Occasionally, if you win raids for White Kyurem or Black Kyurem that open during events, they give you energy to fuse them. You just need to collect that and some candy.

Drop in a less crowded area to gather gear first. AR (Assault Rifle) + SR/DMR combo is recommended. Move inside the zone in advance. Using earphones to hear footsteps is advantageous. Utilize cover while moving, and don't stand still for too long in open fields. Avoid unnecessary engagements and only fight when in a favorable situation.