In order to set the counts per unit, velocity, and acceleration for each axis you must select your axis by clicking the text on the right-hand side of the Motors tab. In Mach4, navigate to Configure>Mach>Motors. There, you will see a list of your Motors on the right: Motor0, Motor1, Motor2, etc. Use the check-box to select each motor you need active. Then, click on the motor for the first axis you want to set up. For example, if you want to set up the axis controlled by Motor0, you click on that motor. This will allow you to enter the counts per unit, velocity, and acceleration. Once you've set your values, be sure to click 'Apply' to save those changes. Select the next motor from the list to continue setting your values for the rest of your axes.  You'll also find a Steps Per Unit Calculator in the Wizards. Simply navigate to Wizard>Select Wizard and choose the calculator from the list.