To start, go to Registration > Discounts. Click Add Discount.
Within the form you'll need to turn on Group Registration Discount
Once the Discount is turned on you'll need to create your parameters.
Example: I want to create an early bird group discount called groupearlybird to be able to have a group of 6 people get 1 of their price tiers for free.
To create this example you will need to set all parameters seen below.
Percentage: 100% off
Turn on Apply to Selected Price Tiers: ON
Select a specific price tier: Group Early Bird 2017
For group registration to work your users will need to:
Buy 5 prices tiers
to Get 1 more at a discounted rate
When you are done set the active from and to and hit save.
For your registrants
For your users they will need to add 6 Group Early Bird 2017 price tier registrations in Group Registration to then apply the code groupearlybird to the last registration to activate the discount.