There are two different ways to add a audio to your message, using a audio URL or upload a audio from your computer.

Using Audio URL

1. Click on flow icon;

2. Choose a pre existing flow or create a new one;
3. Add an Action Set, and click on the attach icon on the bottom right;

4. Click on attach URL;

5. Click on Audio on the drop-down menu;

6. You can insert the audio URL, after that you can call the audio using the variable @extra.attachment_url.

Upload an Audio from your computer

1. Click on flow icon;

2. Choose a pre existing flow or create a new one;
3. Add a Action Set, and click on the attach icon on the bottom right;

4. Click on attach file;

5. Choose the file from your computer.