Instructions on how to do this should be available with your wav editting software. The amplitude of a wav file can be raised using software and a function called Normalizing. Normalizing can be done in any major wav editor. If you feel the need to normalize, you should normalize to the PEAK value and NOT RMS value. You should also normalize the entire show at one time or you will screw up the levels from track to track.
Normalization is only necessary when the peak amplitude levels of a show are very low.
It is in good practice to have at least double that amount of drive space per show, because as you track it you will want to save individual tracks for burning. Consumer audio applications such as Cool Edit and Sound Forge do not do a particularly good job handling hiss reduction especially. There are three major kinds of digital connections. They are the two most common connections you'll find. Coaxial - this is the most common.