These instructions are for the Skylight Calendar product. If you purchased a Skylight Digital Photo Frame, read more about the Skylight Frame here.
When you tap on "Calendars" at the bottom of your Apple Calendar app:
and the Calendar you want to sync is listed under "SUBSCRIBED":
You'll have to go through the special steps below (if the Calendar is listed under another header, follow the basic steps here).
Open the "Settings" app on your iPhone, and tap on "Passwords & Accounts":
Within Passwords & Accounts, tap on "Subscribed Calendars":
Tap on the name of the Calendar that you want to sync, and copy the address for "Server"
Then simply email that link to your Calendar: