- Download the install kit from their website (warning! there is some upselling going on)
- Install the software
Unfortunately there aren't any options to make the program more silent or transparent to the end-use. It is rather chatty and will always prompt the user about things like detected files or updates. Also, it will show an advert after each update. Now there are ways to disable this, however be aware that you might be breaking the license by using them.
To sum up: Avira is a nice little AV with very good detection rates, however it lacks some configuration options which would make it suitable running it silently (to avoid bothering / confusing users). I would recommend going with one of the other alternatives and a layered security approach.