what software you use?
I would...
(use a good mic to record the sound. but its too late in this case, just gotta recover what we can)
if you are rich and can afford waves plugins you could use x-noise to remove the background noise easily and effectively, but i assume you dont have the money for waves plugins.
so...
go through the wave file and chop out all of the sections where there is no speech.
create a small fade in at the start of each wave section and fade out at the end. this will stop the wave suddenly appearing from nowhere.
use an EQ to try and take the wind noise out. it will be in the same range as the voices though so expect to have to choose between vocal fidelity and quiet background.
make a background ambience wave, to overlay the film audio. you can control the background noise and choose sometheing pleasant.(birds singing and such) this will minimise the jump between silence and hissy audio.
further mask the bad audio with music.
go easy on master compression because that will bring out the hiss.
next time use a better mic and a better room.
i personally would scratch that audio track completely and overdub the voices.(good fun)
Sometimes I like to use words out of contents
