Whe you read the book that came with your version of picbasic you will see that some declarations must be made for the LCD.
In the declartions the display driver will know how much pins and where the pins come from.
like this:
Code:
	        DEFINE	LCD_DREG PORTB
		DEFINE	LCD_DBIT 0
		DEFINE	LCD_RSREG PORTB
		DEFINE 	LCD_RSBIT 4
		DEFINE	LCD_EREG PORTB
		DEFINE	LCD_EBIT 5	
		DEFINE	LCD_BITS 4
		DEFINE	LCD_LINES 2
		DEFINE	LCD_COMMANDUS 2000
		DEFINE	LCD_DATAUS 50