Hi -- I'm not sure exactly what you need (are you writing out parts? Or just need to be able to build the chords?), but I'll give it a shot.
In the key of C, the I chord is C E G, and the V7 chord is G B D F.
There are a lot of rules that your teacher might want you to follow for the voice leading, but in general that C chord will be in root position (not inverted) for a proper sounding cadence. The V7 chord might be inverted.
If your teacher gave you a list of rules (like "notes can't move in parallel fifths") your best bet is probably to use pencil to write in the notes you know will be in each chord of the cadence: "C E G" then "G B D F", then check the rules; if you're breaking one, try moving one of the problem notes to another octave. It's often okay to double the root of a chord, if that helps. That is, you might have a cadence like this:
D - C
G - G
F - E
B - C (also nice with this one is that the B and F both get to resolve to a note only a half-step away... which is where they "want" to go, and the D-C line and F-E line are moving in parallel sixths, which is good, unlike parallel fifths or octaves, which is weak)
I hope this helps a bit -- write in with a particular problem that is confusing you, and someone can probably help you out.
-Rob