Nuendo has a help mode. You have to use little scrolling yellow triangles that turn the selected area blue. This will mix down everything within the blue zone, then you go under file and select export and choose what format to export to whatever folder...If you had purchased the software you might know how to use it, but since you probably torrented it and aren't interested in paying your dues to learning it, the help I just gave you will be more than anyone on the site will do.

thanks

by the by sir/madam i did not torrent it . it is just that i am a newbie just learning music and since i am a doctor i am not able to attend classes for learning about it. anyways thanks a lot

All the wave files get stored in the project folder in seperate sub folder. Also you can export the mix to an audio file. Look under the file menu.