Sound Question

Hello :)
I got some gun sounds for a lighting test i am doing, (all my films need the best sound, and of course, guns) and I got machine gun sounds from soundfind. Then I got Dubit (a sound adding program) and synthed the sounds with the film perfectly. But when I went to save it, It didn't allow me :( So i am now wondering if there is any other way to add the sounds. Thank you and good day :)

-Gardias, Director of PickleWeezle Productions