I can't select "Add automatically".

So that customers are never charged without agreeing, Add automatically is only available when the gift product is priced at zero.

Do one of the following.

Set the gift product's price to zero.
Change how the gift is added to Let the customer tick a checkbox or Ask in a dialog.

If How the gift appears is set to Discounted to free, the gift product has a price, so Add automatically isn't available either.

How to add in common settings: add automatically, or let customers choose with a checkbox

Choose how customers receive the gift, Choose how the gift price appears in the cart

解決しないときは

インストールから使い始めるまでの流れは、設定ガイドにまとめています。それでも解決しないときは、お気軽にお問い合わせください。