You will get BPs if you kill your CS by sending your support before your CS lands (only if the city you are supporting is not a ghost town). But if you send your support after the CS lands, you will only have BPs if someone attacks the city you are holding a siege on
I tried to send my CS to attack a city and it said I need to send land troops with it. When I added the land troops it stated that I needed to use transports. How do I send a CS ahead of time before the support if it requires me to send support when I try to send the CS?
To conquer a city you send these units in the same attack
1 colony ship, Offensive land units, At least 1 ls or bireme, and the transports for the land troops
To support your ship you must send a Seperate support that will land after the colony ship lands and clears the city if the ship does not clear the city completly then it will be destroyed and your siege is over.