By considering that you are asking about the Online Bill Service started by Punjab Govt. Treasury, I want to make it clear that this is an online system. We do not require to download this, as it run online from the host server itself.
In other words we can say, Just open the website & then use the provided username and password to login to the treasury Website. After successful login you can submit the bill online. Username & password are provided to the DDO only
by the dealing treasury.
The Treasury Online Bill Service website is http://vpn.punjabgovt.gov.in
For security point of view this website has 2 step login system. After successful login, easy to use & understand menu is available.