I assume that when you say "the front usb ports", you mean usb ports that are accessible from the front of your computer tower, and that they are "in" the tower, but not actually connected to anything else inside the computer.
If this is the problem, I'm imagining that you are building your own computer, or at least reassembling it.
The first thing you need to know is what kind of motherboard you have. Unless you have a rather old computer (i.e. 8 or more years old), my best guess is that there is a "header" (connector) for the wire (usually black and grey) that goes from the circuit board attached to the inside of the front of the computer tower to the motherboard.
Perhaps the more difficult part is figuring out where this cable is supposed to attach to the motherboard. If this is a self-built computer, I'm imagining that you probably know what motherboard type you have (or there is someone that knows), and have a bit of documentation. In short, if you know what kind of motherboard you have, this information should be in the instructions. Trying to identify it by eye is rather difficult -- too many pins and other places to choose from, unless you hook up USB hardware all day.
If you don't know what kind of motherboard you have, it is sometimes written on the board in rather small writing. Google any information that you think might be the brand name of the motherboard.
If all else fails, MajorGeeks.com has software that you can download onto your computer that will/should tell you what kind of hardware you have.