Dan, you need a DC power supply that puts out 12v (usually). Check the fans for voltage and milliamps. If each fan uses 12v and 100mA, you'd only need one power supply that puts out 12v and 200mA. That's in a perfect world. If you find one that puts out 350mA or 500mA, that's still going to work. In my example, you could run 3 100mA fans or even 5 100mA fans, as long as you don't exceed the mA of the power supply.
Wiring them up is easy, and this is how I do it. Strip the wires of the power supply so they are bare. Same with the ends of the fan. Now touch the wires to the wires of the plugged in power supply. If it works, perfect. If it doesn't reverse the wires and test again. Once you know which side touches which side, you can test the next fan and so on. Get all the "A" wires together, twist them together. Get all the "B" wires together, twist them together. Plug it in once more and verify they work. Now you just have to water proof them, and they are ready to go.
Will you put the fans on the top of your tank, or perhaps over your sump? It works both ways. Here they are on the tank's edge in an acrylic frame to keep them from falling in:
And here they are over a sump:
