Help, I want to install a leviton brand wall timer switch.

Currently there is a simple toggle switch in the wall now. In the wall there are only two wires (a white one and a black one). However, the timer that I wish to install was 4 wires coming out of it (a white, black, blue, and green wire).

What wires do I connect to the ones in the wall? Do I leave 2 of the wires on the timer not connected to anything?

This is the only switch that goes to the light I wish to have on a timer (so, it's not a 3 way switch right? ).

What do I do?

Not knowing the model of timer you have, this might not be accurate info, but I Googled around and found that the blue wire is the switched wire (so this goes to your light). The black, white, and green wires are hooked up to the hot/neutral/ground wires in your switch box, as usual.

Here is a wiring diagram I captured that might help.

[After reading your problem again I had another thought]
If your switch box truly has only a single pair of wires (i.e. one romex cable) hooked up like this drawing, then I'm fairly certain you won't be able to use the timer because you don't have a "hot" wire to run the timer's clock. The way your light is wired is that the hot wire is by the light and only the switched side of the circuit is brought down to the switch box. In which case you are out of luck.

Hope this helps.
WallyH