Fans using a 4 pin molex connector will usually be of the type that allows you to daisy chain several to one psu cable.
If not, simple molex splitter cable can be used. You can attach many fans this way.
The 3 pin type of fan connectors will plug into a motherboard 3 pin connector. If necessary, you can buy a splitter cable that will allow you to power two fans from the same 3 pin socket, but you will get speed sensing from only one. There is a limit to how many amps can be delivered by the motherboard socket to the fans, but 2 fans are usually ok.