Hi Alan,
The easiest way is to upload the video to YouTube and then post the link to the YouTube video on your AVoYP post. If you post the link on a new line it should embed rather than showing the link.
To upload videos to YouTube have a look at this wikihow explaining the process with pictures.
Note: When you upload the video to YouTube you want to set visibility to ‘Unlisted’ not ‘Private’. ‘Private’ makes it visible only to you. ‘Unlisted’ makes it visible only to people who have the link that you would share here. It would not show up on your channel page or in any search.