Instructions
Defeat the Airship boss, Evrae. You and your group will then be led onto the Bevelle premises, just before the temple. Run toward the temple.
Fight the swarm of enemies that arrive immediately upon heading towards the temple. Kill the enemy with the flamethrower in the middle first. Move ahead, fighting your way through the throng of enemies.
Fight the Machinas closer to the temple, killing them first before other enemies. Note that the YKY-63 Machina are weak to water and fire, not thunder. Also note that this kind of Machina knows the Thrust Kick, which can put a character out of the game if used.
Reach the YAT-99 Machina. Kill the surrounding guards first. Kill the YAT-99, unleashing everything you've got. Watch the cutscene that occurs after successfully defeating the enemies and enter the temple. Take note that after playing and completing the Bevelle Temple, you cannot go back inside again.