On Ticketleap, you can create a Buy One Get One (BOGO) function by restricting the number of tickets for a ticket type to a minimum of 2 and a maximum of 2 per order. You then set the per ticket price to be half of what you would want the BOGO offer to be.
To get started you can either add a ticket or edit an existing ticket type under your event's Details tab.
Once the new window has opened up to edit the ticket or add the new ticket enter the new information for the ticket.
You'll need to enter the price to be half of what you would like to charge the buyer. For example if you wanted it to be buy one for $20 get one free, you would set the price to $10 per ticket.
You'll then need to check the Restrict Number of Tickets per Order option under the More Options section. To do a BOGO you need to enter a minimum of 2 and a maximum of 2.