You can include an mp3, aac or wav file directly to your listing page and / or a SoundCloud link. You also have the option of including a video by adding a link from YouTube (please note, you cannot add these to your profile, only the listing for the service you are offering).
Once you have logged into your AirGigs account, click on My Services (which is in the Seller dropdown menu).
If you already have a service created, click on Edit Service. Otherwise, to create a new listing, click on ADD NEW at the top of the page.
Towards the end of the page, you will see this section that allows you to add an audio file, SoundCloud link and an optional YouTube video:
Once you have included all the relevant data, be sure to click on the blue Submit button in the bottom right-hand corner of the page: