You can install beorg from the App Store to your iPhone or iPad.
When you run beorg for the first time you need to:
Provide permission for beorg to access your calendar. This will allow beorg to display calendar entries alongside dated items from your files.
Provide permission for beorg to access your reminders. This will then appear on the Agenda and Tasks tabs.
Choose how to synchronize your org files. iCloud, Dropbox, Box, a folder from another app or WebDAV can be used. If you are starting from scratch, and use macOS on the desktop, then iCloud is recommended. For other sync methods you’ll need to configure those later on the Settings tab. By using folder from another app you could keep your files completely locally on your device.
With iCloud no further setup is required. If you want to use another sync method you’ll need to make sure you’ve got a folder ready in which to store your files.