User menu: How do I define the liquidCrystal in my custom library? (1602)

Other Hardware Displays
5 
LiquidCrystal *lcd;
Menu menu1(lcd);

Having it like this in my sketch, I'm able to upload it. But obviously the arduino doesn't know the pin connections. Where should I define these?
I've tried things like Menu menu1(lcd(4, 5, 6, 7, 8, 12)); but with no luck...
testbestand_leds11.ino:17: error: 'lcd' cannot be used as a function Is the error I get.

Using the "Glyphduino" library; I managed to find my mistakes.
It should be as following:
Constructor:

Menu::Menu(LiquidCrystal *lcd){
this->lcd = lcd;
	this->lcd->begin(16, 2);
	this->lcd->clear();
}

Header:

class Menu
{
private:
	LiquidCrystal *lcd;
public:
	Menu(LiquidCrystal *lcd);
};

Sketch:

LiquidCrystal lcd(4, 5, 6, 7, 8, 12);
Menu* menu1 = new Menu(&lcd);

void setup() {
	menu1->printMenu();
}

Thank you Oliver for helping me out!