Depends.
Simplest and cheapest solution would be too use the adapters that no doubt came with your fans to plug them into the PSU, but that has a downside of having them run at 100%, so not the best for noise. There are adapters you can buy that change the voltage so they will run at various relative speeds.
Next would be splitters, which is where one fan plug splits into multiple. You will have to be careful with splitting off a mobo, too many fans and you can burn out the mobo.
Or a fan controller, which the name implies allows you to control the fans between any speed you want and typically offer enough Wattage per channel to have multiple fans on the one channel (through the use of splitters).