If they landed, I would not assume that they may not be coming out of altruistic reasons, or to just say, “Hello”. It would also be very possible that they could bring alien bacteria that could kill us, or that our bacteria could kill them. All in all it would probably not work out well.
But if they did, and it was a peaceful encounter with no passing of deadly germs from one to the other, then it would be a good opportunity to evangelise them and teach them about Christ. Perhaps we could send missionaries back with them?
But realistically, if there is other intelligent life in our vast universe, and presuming that somewhere there is a species considerably more technologically advanced than us, then haven’t they showed up before now?