Getting started:
To get started, click here to download the (DEB package).
When Software Center opens, click ‘Install’
After installing, go to Applications –> Accessories –> avast! Antivirus.
Click the link below to obtain a license key.
Type the license key and click OK.
The first thing to do is click ‘Update database’ shown above.
When done, select to scan the ‘Entire system’.

To get the best result when using avast, launch the program as root or administrator. To to that, press Alt-F2 on your keyboard and type the command below:
gksu avastgui
Enjoy! And please come back soon.