Power off the switches. For each switch in the stack, connect stacking cables from the bottom stacking port on the first switch, to the top stacking port on the next switch.
On the last switch connect the bottom stacking port to the top stacking port on the top switch.
Power on the the switch that you intend to be the primary switch first and wait until you can manage it. Once you confirm the primary switch is manageable power on the each of the remaining switches one at a time until every switch is powered on.
They will add themselves to the stack.