cout << mArray.display;display is a function. You need to add parenthesis. It also wants a key and a value as its 2x parameters. But what do you actually want display to do? I imagine that a display function would only take in the key, and then give the value. It's kinda defeats the purpose for the map to need both the key and value. Your remove function doesn't have any code, so I'm not sure what you want it to do, but I would say the same thing there, it's redundant to require both the key and value for displaying or removal.
your insert function always inserts the data into aData. Is that intentional? Sounds like you might want another variable to keep track of where you are in your internal array.
What do you actually want to happen in remove? Should the size variable be decremented? Should the array itself be re-allocated but without copying over the the given element?