First, you'll need a YouTube account. If you have a Gmail address or Google account, you've already got a YouTube account, you just have to sign in using your Google log-in and password.
Once you're signed in to your YouTube account, all you need to do to upload your video is click the Upload button on the top right of the page, add a description, and you're all set.
Make sure you only upload videos which you own, or which you hold the publishing rights for.
YouTube has a lot of helpful tips, tricks, and advice in its Help section, and can guide you on technical issues like sound quality and video resolution.