why can’t I use my modem?

I have ‘installed’ a new modem from Zoom. It’s an internal 56K Duelmode. Did all the proper things……..I thought! When I try to log onto the internet…..my IP says the modem is not responding, or has not been installed. Is there a secret to the installation? A ‘teckie’ told me to install the software first, then the modem. Didn’t work. Now what do I do?