Delete one occurrence or the whole series

Short answer

Open the entry on the calendar and choose delete. Full steps below.

Steps

1. Open the entry on the calendar and choose delete.
2. Choose Only this one to remove a single date, or All repeating entries to remove the whole series.

Still stuck?

If a step does not match what you see on screen, stop there and open a ticket from Support > My Tickets with a screenshot of that step. The team will look at the account directly.