Pico - Arduino Board

I am working on this board for a project at school.

It is a very simple question but maybe I am doing something wrong on my setup.
I would like to use 4 digital outputs and 3 analog inputs.

For the 4th digital, I am using pin 1 (RX). I dont use serial.print(). And I have nothing wired to pin 1 while uploading my sketch. Still, RX won't work as digital output, even after pinMode(1,OUTPUT).

Any suggestion what to try next?

Thanks in advance

The PICO does use an ATmega32u4 (same as Leonardo and Micro).
So Serial.print does not interfere with D0/D1 (RX/TX) but with the USB port (Serial USB).
To use the serial pins (D0/D1) you would use Serial1.print.

Please show your code.

Thanks for your answer

I am just migrating a working example from arduino UNO to PICO
in UNO, address for a stepper motor pins are 8,9

AccelStepper stepperX(AccelStepper::FULL2WIRE, 8, 9);

And I am just trying to use:

AccelStepper stepperX(AccelStepper::FULL2WIRE, 1, 2);

Where pin 1, is the RX.
For clarification: Same line above using pins '2, 3' or, '3, 4', works fine.

My ideal setup for 2 stepper motors would be something like:

AccelStepper stepperX(AccelStepper::FULL2WIRE, 1, 2);
AccelStepper stepperY(AccelStepper::FULL2WIRE, 3, 4);

To use the serial pins (D0/D1) you would use Serial1.print.

I am afraid it means I would have to Serial1.print a char related to whatever the library is sending to the motor pin?