First of all, run the Voice Memos app.
1. Choose the voice file and tap in the left corner.
2. Select Send Anywhere from the list of apps. If you can’t see Send Anywhere, tap ‘More’ on the far right of the list. Then enable ‘Send Anywhere’
3. 6-digit key will be created right away! If you want to send directly to a device, choose a device displayed below the 6-digit key, the notification will be sent to the receiving device.
Due to the nature of iOS operating system, the screen should be kept on until the recipient downloads the file. Be careful not to turn off the screen.