As ever, you need to break the problem down into its component parts call them "subsystems" if you like:

1. Receive a character from the serial port

It really makes no difference what will happen to the character afterwards - reading a character from the serial port always works the same way.

There are plenty of tutorials & examples on using the serial port.

2. Display a character on the LCD

Again, it really makes no difference where the character came from - writing a character to the LCD always works the same way.

There are plenty of tutorials & examples on using LCDs.

3. Join them together!