There are several ways to record this message: You can do so on your mobile device or desktop. Save the file as an MP3 file. Here are some helpful links:
To convert your file to MP3 file, go to: https://online-audio-converter.com/
STEP 1: Follow the menu path: Settings :: Phone :: Lines
STEP 2: By pressing the gear shaped Actions icon and opening the Actions menu, select Manage Lines
STEP 3: Navigate to the Routing tab. A popup will appear which will allow the file to be replaced
STEP 4: Delete any existing greeting by pressing the Delete button next to Message 1 field
STEP 5: Once the file is deleted, select Choose File in the Message 1 field and select your new greeting message from your computer
STEP 6: Click the Blue check mark.
STEP 7: Press Lines Edit button at the bottom of the form to save your changes.