How do you add 'Buy 2, Get 1 Free' option button like this?

[Tommy0227]

Hey I was trying to add Buy 1, Get 1 free button like the first picture, but I couldn't manage to.

I know there is a setting for But x Get y free, but I want it to appear as an option button like in the picture(does not have to be the exact format, but a similar function).

Does anyone know how to without paying? The second pic is my store and the theme is Refresh.

My store

[Tommy0227]

Hey how can I send you a message?

[Tommy0227]

I couldn't find any button to message you in your profile..

[Tommy0227]

Hey I couldn't find any button to message you. How can I message you?

[Tommy0227]

I texted you, could you check?

[Em3]

Im also looking to do something like this. could you tell me how you did it?