If you could have your oc added to the books, where would you add them?

What i mean is, let's say that you get the opportunity to have your oc added to the main series, either as a side character or just a background character, where would you have that character? Ether as a random shopkeeper or a new friend of someone like Peril.

As an example, I would have my oc Modrý, as a gardener on Dungeon Isle, he would be introduced by someone, Modrý would then give his story as how he, a Rainwing and Nightwing hybrid arrived on the isle,