#1
I have this program "audacity" but all of my recordings are very quiet..

so what´s wrong?

any tips?
#2
Turn up the mic gain.

And it depends what your recording with, and how the volume of what your recording is.
#3
try changing the 'gain' of your mic. You want to have your record levels at the peaks just below the max. This way you get the most sound dynamics and no clipping.

Succes