Both. You can come and do the workshop before the birth. You can take your wrap to the maternity ward and then carry the baby from the very beginning if you wish. In case of caesarean section, anaesthesia, prematurity... this allows the father to carry the newborn and to provide him with a transition and an accompaniment that meets his needs in more comfort and softness and to reduce the temporary break with the mother.
You can also do a workshop after the birth and come with your baby. This will give you the opportunity to see things in a more concrete way. Many instructors offer packages with several workshops and can follow you at different times.