How to record my voice when making a video using a headset?

I'm making my own youtube channel and like all beginner channels start off small so in using my iphone to record video but when I talk in the video my voice sounds like there's no quality and I was wondering if there was a way to record good quality voice while I'm recording a video also. Maybe using a mic?
… Sorry if that was confusing but it is confusing.

Yeah. Pretty much just get a headset/mic and plug into the iphone's headphone jack. If it's compatible it will work just fine