Roguelike Array question

Hello constructors,

i have a tiny problem with arrays.

I'm currently creating a rougelike game with this tutorial by SupremeRobot:

https://www.scirra.com/tutorials/1123/smarter-procedural-roguelike-dungeon

I'm not very good with arrays and have a question for someone of you who's better with it.

I want to target a specific location on the map to create a special room there. How can i do that?

Example: I want to have a spawnroom in the Middle of the map. So I'd have to override the type in that space of the array with another type... how?

thank you!