When a man impregnates a woman. The "club" stands for the woman or her private parts, and the shooting implies the man ejaculating. The context it is usually used in is when the man and woman aren't legally married.
"Kanye this is what happens when you date a chick with such a past, you knew what that hoe was like, but you still wifed her and shot her club up"
This is a quote from American Radio show host/Personality Charlamagne Tha God (1051BreakfastClub), who uses this phrase often, when he heard Kanye West reply to Ray J new single "Hit It First" where Ray J talks about having sexual relations with Kim Kardashian before Kanye West did.