Catch a Charcadet in the wild or receive one via trade or breeding.
Level up Charcadet until it reaches level 38.
Ensure Charcadet is evolved while holding an appropriate item:
If it has a Fire-type evolution, evolve it into Armarouge by using the Auspicious Armor.
If it has a Psychic-type evolution, evolve it into Ceruledge by using the Malicious Armor.
Use the item on Charcadet before leveling it up to level 38 (or keep it held until it reaches level 38).
When Charcadet reaches level 38 with the correct armor equipped, it will evolve automatically.