Finding the Calendar feed URL in your AppointmentGuru account:

1. Login to the AppointmentGuru web app.
2. Click Settings and then For your phone, copy the calendar address on the page.

Once you have the link, you can add it to your calendar of choice. Two things to remember:

1. It's a read-only calendar, so you won't be able to add appointments and expect it to sync back to AppointmentGuru.
2. Some calendars take a while to sync (especially if add your calendar via a Google Calendar, changes are only visible after 24 hours).

Add the Calendar to your iPhone calendar app:

1. On your iPhone, go to Settings > Calendar > Accounts > Add account > Other > Add subscribed calendar.
2. Paste the Calendar URL.

Add the Calendar to your Android calendar app:

1. Follow the steps to add the Calendar to your Google Calendar (on this link).
2. On your Android device, open the Calendar app and tap on the three dots on the top right > Calendars to display > Calendars to sync and check the box next to your calendar > OK.

To beat the 24-hour delay in updating Android with Google Calendar, you can search the Play store for an app that forces updates to your calendar more frequently.