Setup on iPhone

Launch the Settings app on your iPhone or iPad.
Tap on Mail, Contacts, Calendars.
Tap on Add Account... under the Mail section.

Launch the Settings app, tap on the Mail, contacts, calendars button, and then tap on the Add account button.
Tap on Other.

Tap on Add Subscribed Calendar under the Other section.
Enter or copy in the server location of the calendar. https://calendar.google.com/calendar/ical/byslcalendar%40gmail.com/public/basic.ics

Tap on the Other button, tap on the Add Subscribed Calendar button, and then enter the server location.
Enter any username, password, or SSL info you need to. Most times you don't have to with public subscriptions.

Tap the Next button.
Tap the Save button.