SOLVED
I followed this tut: http://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/Intro_to_Bezier_Curves#Extruding
I finished extruding the filled curves, but when I try to use the Decimate Modifier, the Decimate option does not show on the modifier list. Any suggestions?
EDIT: I realized I had to convert the curve to mesh.