Set up iCloud Сalendar synchronization with your Bitrix24.
Go to the Calendar section and click the Synchronize button.
Click Connect in the iCloud calendar block.
Log in to your Apple ID account by entering your email address and app password. Then click Connect.
Read more information in the article: Add an application password for the iCloud calendar.
Click Continue and make sure that all events in calendars are synchronized.
Create an event in the iCloud calendar and it will automatically appear in Bitrix24 calendar.
Read more in the article: Disable calendar synchronization with iPhone and macOS.