These displays are usually able to display 16 characters per line on 2 lines (16x2), but other formats (notably 20x4) are also available

Connect to the Pico as follows:
| Circuit | Connection |
|---|---|
| VCC | Battery + |
| GND | Pico GND |
| GND | Battery - |
| SCL | Pico GP5 or other SCL pin |
| SDA | Pico GP4 or other SCL pin |
You need to add the lcd library. Copy the lcd folder from the lib directory on github to the lib directory on the pico:
Write this code and download to the Pico.
See code on github# 16x2 character LCD test
import board
import busio
import time
from lcd.lcd import LCD, CursorMode
from lcd.i2c_pcf8574_interface import I2CPCF8574Interface
# Set up LCD display
i2c = busio.I2C(board.GP5, board.GP4) # SCL, SDA
interface = I2CPCF8574Interface(i2c, 0x27)
lcd = LCD(interface, num_rows=2, num_cols=20)
lcd.set_cursor_mode(CursorMode.HIDE)
lcd.set_backlight(1)
# Single line
lcd.clear()
lcd.print("abcdefghijklmnop")
time.sleep(2)
# Double line
lcd.clear()
lcd.print("Line 1\nLine 2")
time.sleep(2)
# Position
lcd.clear()
lcd.set_cursor_pos(1, 4)
lcd.print("Here I am")
time.sleep(2)