I presume you connected the CPU fan to the mobo pinout identified as CPU_FAN. If all your other case fans have Molex male connectors on them, you must connect to matching Molex connectors on the wires coming out of the PSU. These days th4e only devices that need Molex power inputs are IDE HDD's and Optical drives, so you may have spare Molex's available. But if not, get a simple 1-to-2 Molex adapter that makes more connectors for you.
Did the case and its fans come with a speed controller? In that case you could use the adapter to convert the one controller output (if it only has one) to two for the two fans. If you have no controller, you can buy one from a computer parts shop and use it to set the case fans speeds manually to some mode that gives you good temperatures inside your case and moderate fan noise.