You'll need VirtualDub (available here)

1. Open VirtualDub
2. File - 'Open Video File...'
3. Select the file 'Wicked.City.[XVID]-Rusty.Monkey.avi'
4. In the 'Video' menu, select 'Direct Stream Copy'
5. In the 'Audio' menu, make sure 'Direct Stream Copy' is also selected
6. Also in the 'Audio' menu, select 'WAV Audio...'
7. Select 'all files (*.*)' as file type
8. Select the file 'Wicked.City.English.Dub.mp3'
9. Go to File - 'Save as AVI...'
10. Enter a new filename (you can't overwrite the old one, it has to be a new filename)
11. OK, now wait for VirtualDub to have finished, and you should have a new dubbed videofile!

Good luck!