Hi, PHFM, welcome to the forum.
It would be best to start a new topic in this sub forum; the "new topic" button is near the top right of the thread list.
In this thread please list your OS, Avast version installed, any previous AV or firewall installed, even if removed, and the name of the program you've downloaded, plus any information about messages displayed regarding blocking of same. Where did you get this downloaded program that is blocked?