changing average decibel level of a recording...

[Guest akanalog]

i have been told i need to have the average decibel level of a piece of recorded music at -12 dB for a particular project. i am using a macintosh. the piece of music is an aiff file from a CD. i am looking at it right now in this program called audacity and it looks like the average dB level is probably lower than -12. i have no idea how to use this program and how i can alter the average dB level. i also have a copy of bias peak which i don't know how to use. would audacity or peak do what i need it to do? anyone know any other programs for mac which could do what i need? i do not have anything nice like pro tools and i am pressed for time. thank you.

what is this even called, changing the average dB? is this equalizing? compressing? normalizing?

thank you for any help.