Another posting already discusses how you can change the pins to use spare stepper controllers for broken controllers by changing the pin layout. Assuming you are using a RAMPS board and using Marlin firmware, you should look at the pins_RAMPS.h file.

This file requires changes to address E1 to E0 and vice versa, please edit the file so that:

#define E0_STEP_PIN        26
#define E0_DIR_PIN         28
#define E0_ENABLE_PIN      24
#define E0_CS_PIN          42

is changed to:

#define E0_STEP_PIN        36
#define E0_DIR_PIN         34
#define E0_ENABLE_PIN      30
#define E0_CS_PIN          44

and also change:

#define E1_STEP_PIN        36
#define E1_DIR_PIN         34
#define E1_ENABLE_PIN      30
#define E1_CS_PIN          44

to:

#define E1_STEP_PIN        26
#define E1_DIR_PIN         28
#define E1_ENABLE_PIN      24
#define E1_CS_PIN          42

When the file is changed an saved, build and upload code to your board and plug the connector of the E0 stepper into the E1 header.

I wanted to expand on the great comment by 0scar and explain what's the fastest way to change pins. I know this is an older topic, but for the sake of people looking for an answer, I figured I add this.

First of all it's easiest to change the pins in the pins file for your specific board by simply renaming E0 to E1 and vice versa. This is much simpler than copying and pasting the pin numbers per pin. Only do this when swapping entire driver pin lists as this gets quite confusing when switching around only certain pin numbers.

Second, and this is a big one: don't forget that when you use drivers that are capable of sensorless homing, and when you use that technique, you also have to change the _DIAG_PIN settings or else the sensorless homing won't work correctly.

the fastest way is to slice using two extruders and assign all print work to E1.
Set the head offsets to [0,0] and that shall do the job.

The harder is to edit pins file and do remapping.