"...there are only 2 black wires, and 1 copper wire (ground). The instructions say i have to hook up the white wire to a set of white wires in the junction box. but there are no white wires in the junction box."

I'm a bit confused by this description. Did you mean that there are 2 black wires, 1 copper wire and 1 white wire?. That's what would make sense.

Assuming that's the case, here's the deal:

There are a couple of ways switches can be wired. One way is that the power feed first enters the switch box with both a hot (black) and neutral (white). The neutral is simply passed on to the fixture (i.e., the incoming white is connected to the outgoing white). The incoming hot connects to the switch and an outgoing hot goes to the fixture. (So, two wires in, two wire out, right?)

A second way is that the power feed goes first to the fixture. The white (neutral) connects directly to the fixture and the incoming hot goes to switch along with what we'll call a "return" wire. This is known as a "switch loop" and it has no neutral. One wire is "always hot" (the feed) and the other is the "switched hot" because it only gets power when the switch is on.

[There are a couple of other ways to wire a switch, but these two are the most common.]

A simple switch does not consume power itself. It only connects the two wires then it is closed ("on") and disconnects the two when it is open ("off"). The problem arises when a more complicated switch needs power for something. For example, a switch with a pilot light or night light consumes power itself and so it needs a neutral. Ditto with some timers. You cannot wire a switch that is itself a power consumer to a simple switch loop, which is apparently what you have.

So, there are two possible solutions. First is to do some rewiring to bring a neutral into the box. One way to do this is replace the switch loop cable (two wires) with a three-wire cable, one of which will connect to the neutral at the fixture. Since you're not familiar with wiring, I won't elaborate on how to do this, or other ways this can be accomplished. You'd probably need an electrician.

A second possible solution is to find an old-fashion mechanical timer that doesn't use electrical power itself. (It's basically a switch with a "wind up" spring.) This assumes, of course, that your intended purpose is just to let the fan run for a while and then switch off by itself. If your objectives are more sophisticated than that, I'm afraid you're SOL.

Good luck.

I think he means there were only two black wires and one ground existing in the box. If so, is his box piped in or is one of those wires actually a white wire with black tape on it?

I'm assuming he has just a switch leg going down to the switch, which means he can't use his timer since he has no neutral.

Thanks, foto'. Yeah, you're right and I see that now after re-reading. The "only" part refers to the switch leg wire, not the device.