Go through the following steps to create BOGO offer.  

Step 1Install App

Install Discount Box app -> Open Admin panel -> Click on "Apps" tab -> you will see Discount Box app listed as shown in Image.

Click on this listed Discount Box app.

Step 2: Go inside Discount Box app

# When you go inside the app, you will see 3 tabs on top which are Dashboard, Setting & Create Offer.
# Click on Create offer button from top 3 options, you will see options like below image.
# Now click on Create Offer button of Buy X get Y. 

What is Buy X get Y offer?

It is also called BOGO offer.

BOGO is one of the best "ideal" offers you must have in your store. Make Offer with BOGO when you want to produce more money. It is not beneficial for shoppers only. Merchants can clear out flat products with this offer type.

This offer type will allow you to create a discount in 3 varying ways.

1. Select product X with minimum Qty & get Z % off on fix Qty of product Y.

Example: Buy 3, get 10% off on Shoes.

2. Select product X with minimum Qty & get $Z off on a fix Qty of product Y.

Example: Buy 2 "Red Skirt"& avail $12 off on "Nike Shoes"

3. Select product X & get product Y absolutely FREE.

Example: Buy "Black top" & get "Blue Denim Shirt" absolutely FREE.

Note: You can apply different kinds of discount on product Y, Customer will not get any kind of discount on product X in any criteria.

Step 3: Create Offer 

-> To create offer select Buy X get Y offer Type from DropDown box.   

-> Choose products or collections that trigger this offer when added to a cart.  

(Select product/collection through which you want to apply discount on another products.)

-> After that, select products/collections on which you want to apply discount as shown in below image.

( BOGO lets you create an offer that activates when a specific criteria is met. You can either add a single product to the cart at a discounted price, or display a popup with a list of multiple items or collections, each showing the discounted pricing.)

Step 4: Advance Settings  

-> There is also an settings of Offer message texts. These messages will display when product added to cart & offer applied successfully.

-> Do additional configuration to customize your offer. You can set a start date & end date of the offer. All these options are optional.  

-> Do not forget to click on SAVE button to save all the settings.

In your store, this offer will display like below image.