I have downloaded and installed, it seems pretty cut and dry but doesn't appear to be working the way I thought it would.

I have the address' set up in BIS, and have clicked on bbreply to set the "name & address" [my name & email address, right?] but when I reply to an e-mail from my secondary email address set up in BIS it does not use that address as my "from".

Am I right in thinking that this software is supposed to change the "from" address so it shows from the seperate accounts you have setup in BIS e-mail setup?

Or have I configured it wrong????

Yes, you are wrong. It only changes the reply to address as the name implies.