You can download a free source program by the name of AUDACITY. It is kind of like Sound Forge or Wave Lab.
My first question is, Do you see any type of waveform when you record using the mic?
If so, do you know how to share the vocal (speech) track to iTunes? In the share menu on the task bar, just choose send to iTunes. You can find the track within Finder,Music,iTunes Folder,Your Name
You record the speech track with Garageband. To do this, you create a new track in the track menu on your task bar. GB will ask you if you want a software instrument or real instrument. You should select real instrument. Your mic should be connected into the audio input ( the port with two arrows pointing inward). Make sure the track is armed. You will see a red light checked on the track . Now just hit record and speak!
If you hear an annoying click, go to the control menu on your task bar, and turn metronome off. Also, in this menu you will notice count in. Select this because it will give you for counts to prepare for recording. After you get your track like you want it, share to iTunes and then grab the file from the iTunes folder and drag it into Audacity.
In Audacity you can add effects to the track or boost the volume level. Go to the edit menu on your task bar and select submenu, select all. Then, select the effect menu, and then amplify. Raise the sliding meter until you can hear the mic. Let us know how it goes. You might be able to clean it up slightly with noise removal. I am not sure. I hope this helps.