We do not recommend higher than 1.5Amps (or a value of 1500). Motors can be damaged. We normally start at 1A (or a value of 1000).

See the comment to the right of the semi colon? On the line with command M906

Change X Y Z values to 1500. That means 1.5 Amps to each axis motor.

Extruder currents are the E settings. A colon separates extruder 1 and extruder 2. Keep the syntax (format) E1500:1500

Select '"Save Changes"' and reboot the Duet. The Duet will read config.g on startup and your new settings will be in effect.