currentStep is just a node in your InfoPath's form schema. It won't ever be displayed on the canvas. You will use it to control conditional formatting in the form, and set the value of currentStep via rules.
So for example, when a user clicks button1, set a field's value for currentStep=1.
When a user clicks button2, set a field's value for currentStep=2.
You can then have 2 sections: one gets hidden when currentStep=1 and the other gets hidden when currentStep=2.
Hope this helps!