Maytag Stacked Electric Washer/Dryer Combo?

i don't know the model cuz we barely moved here and the owner left it. for the washer i wuz wondering where do we put the detergent in. There's this hole in the middle but once we put the detergent in there and washed it the soap kinda still remains there a little. It doesnt' get get out like the whole soap there's still like remainings of the soap still left in the hole in the middle. if any1 can help me that'll be great thx very much!!!