Thank you very much. I already catch my error. I'm new to the sprites world. I was trying to create a tileset from a non-tileset asset pack. In my naivety, I thought all assets could be use as a tileset, lol.
I will try to do my best to create a map using the invididual files. I swear I could not find any asset pack near good as this one in interiors section!
Thanks again.