Adding tiles to a vector2 array

I’m having a lot of trouble with this. I’m trying to add groundTiles to a vector 2 array so I can pick a random position and spawn player and enemies. I’m not at my computer currently(at a friends house so I can’t paste my code I have so far) but I’d appreciate any help I could get. I may just be misunderstanding how arrays work with tilemapping but I’m stuck. Any help is greatly appreciated. Thank you