Interfacing 20x4 character LCD with LPC54628
It's already interfaced electrically if you connect the module to the I2C port.
So seems like you want some kind of software, in which case  you can either read the HD44780 and PCF8574 datasheets and write your own, or use a search engine to see if someone has done it already.
If you're using some oddball language or whatever, you can try porting some source code that is available.