Making my comment an answer just to get this off the unanswered list.
The location of the Auspicious Armor can be found on the site. To be more specific, in Zapapico, there is a man (or woman in Violet version for the Malicious Armor) standing near a small water fountain. There will be yellow text above them saying "Fancy a trade?"
To actually use the Auspicious Armor for evolution, you have to put Charcadet in your party, open up the bag, go to the other items section and scroll down to the Auspicious Armor. Charcadet should light up with the text Can Use under it as you hover over the item, and clicking on it (the armor) will give you the option to use it. Select Use This Item, select Charcadet, and Charcadet should evolve. It basically works like an evolution stone.
If you're confused with the Malicious Armor, since that is a Violet exclusive item, then you can either get someone to trade a Pokemon to you while holding the item or you can trade/transfer Charcadet to a copy of Violet, evolve it there, and then trade/transfer it back to Scarlet.
