How to record audio and send it to mac?

I have to make a movie trailer and I got to record my voice so I can put it OVER the video.
I'm using iMovie which was preinstalled on my macbook pro.
I have an iphone but the voice memo's app is no longer on my phone. (Don't ask how.)
What can I do to get my piece of audio on my computer?

Use Garageband.
Set up a new instrument and set the input as the built-in microphone.
I'm assuming since you have iMovie preinstalled you have a macbook which should have a built in microphone.
Then export to disk and import into iMovie.
or if you want to go with the iphone route download another free voice memo app - I use "Voice Plus".