Whether or not you're home during your clean it is up to you. When you make a booking, you'll be prompted to leave security notes with details on how to access the property. If you feel comfortable leaving a key somewhere secure, there's no need for you to be home.
Alternatively feel free to stick around during the job, whatever you're most comfortable with is fine.
Don't worry! All home cleaners undergo a background check and as an extra precaution we only allow them to see the security notes 24 hours before the job is scheduled to go ahead.