What Arduino are you using? If an Uno or Nano, or other board with only one hardware serial port, one would use a software serial port for a second serial port. There are a few different libraries for that. SoftwareSerial, NeoSWSerial and AltSoftSerial to name a few.
For other boards with multiple hardware ports like the Mega, just use one of those ports.
I would use the first hardware port for the serial monitor and program upload and debug and the second (hardware or software) port for the display. Note that software serial will most likely not work at more than 38400 baud.