Open the Calendar app on your iPhone
Tap Calendars at the bottom of the screen
Find the calendar you want to share
Tap the info icon next to that calendar
Tap Add Person
Enter the person’s email address
Tap Add
Tap Done
Make sure the calendar is an iCloud calendar
Turn on iCloud Calendar in Settings if needed
Use a shared calendar link if you want to share with multiple people
Manage sharing permissions from the same calendar settings
Remove a person by opening the calendar settings and tapping their name