This configuration is performed for Buy One Get One promotions, where you can select which SKU will offer the gift.

1. On the Promotions & Taxes module, access Benefits.
2. Click on New Benefit.
3. Click on Buy One Get One.
4. Fill out the fields according to the article How the Buy One Get One (BoGo) promotion works.
5. At What kind and amount of discount, select the Gift option, and fill it out the field by selecting the SKU to which the promotion will be applied;
6. There is the possibility to Activate gift multiplier to determine whether it will be a gift per order or per purchased item.
7. Click on Save.

In this promotion, the Gift will appear on the product page.