Every Android phone is associated with a Google email address. This may be an email address that you actively use, or may be an email address of which you may be unaware.
You can find this email address on your Android phone or tablet by clicking on Settings and then scroll down and click on Google (Google settings). Your email address will be shown at the top.
Use this Google email address to sign into your Google account and add the Caltrics webcal ics URL.