I apologize for the delay in responding, and thank you for posting. Don't worry, everyone starts somewhere! For a master or for handing off to a mixer, use uncompressed PCM audio at 48 kHz, 16-bit or 24-bit. That keeps full quality.
For a version to upload online, AAC at 320 kbps, 48 kHz, inside an MP4 or MOV file, is a good standard. If you have more questions, our Editing & Post-production and Sound forums are great places to ask.