Register by email to get the free Licence key at:

Browse to:

Or clicking the link you got by email.

Choose you'r .deb 32\64-bit and download.

Give permission to execute by:
Right click > Properties:
Permissions tab > "allow this file to run as a program". - Properties_001.jpg

Execute the file by double click or use terminal.

After a long list you skip or read.
BitDefender Antivirus Scanner for Unices_002.jpg
type in: "accept" > Enter

Enter the Licence key.
BitDefender Antivirus Scanner for Unices_007.jpg