Send to messenger plugin during payment

Hi, Can anyone help me to understand how to add this plugin?
Leota_-_Checkout

You can check this here https://shop.leota.com/1567692/checkouts/4e2c5c71b2f902f27a5e78d72506a879?previous_step=shipping_method&step=payment_method

I’m not sure which plugin you are referring to? That cart does not appear to be hosted by Infusionsoft.