How do I record on MBP with bilt-in mic and avoid noise?

I am recording my own voice for a kid sing along on my macbookpro. I am using Audacity with the built in mic. I get a terrible amount of noise, just crunching aluminum foil, crackling and popping. I have researched a lot of blogs and google etc. and I know I must be doing something obviously wrong. Can someone point me in the right direction? (I am of the mindset, hear hoofbeats – think horses not zebras.) Thanks, RN