How do you fix the clutch spring on a 1996 Geo Metro?

If you are referring to the little springs inside the clutch assembly itself, you don't fix them, you replace the clutch.

See:
http://wiki.answers.com/Q/How_do_you_replace_the_clutch_in_a_96_Geo_Metro

If you mean anything else in there with the clutch, see the above anyway, that'll get you inside.