A booking can not be transferred (to another host)
You need to cancel (penalities will apply if cancellation reason is not a "major dispruptive event") if you can not keep the booking, then guest will have full refund and can book other accommodation.
Or contact Airbnb support for specific advice, depending on the issue why you can not keep the booking.
Am I right in thinking that you have booked a place as a guest and you would like to transfer your booking to someone else?
Are you within the hosts cancellation window? There isn't anyone here who can help you with this, this is an Airbnb forum so it's just hosts and guests but you can contact the host to see what's possible but Airbnb's policy is that the person who booked a stay has to be present during the trip as third party bookings aren't allowed.