how do i delete a calender i the Calender app

Open the Calendars app. Tap on the "Calendars" button at the bottom center of the app. Tap the encircled "i" to the right of the calendar you want to delete. Scroll to the bottom of the desired calendar and tap "Delete Calendar". This should delete the desired calendar

iCloud isn't my specialty but try settings> iCloud> calendars> on, on both devices.

You're welcome. Glad to help.