New install

I have been installing the e-commerce module and everything seems to be fine but authorize.net never appears.

All I get is paypal. I have googled and read and looked for some separate module, but I'm stumped. Can someone please help me by nudging me in the right direction? I have reinstalled drupal from scratch and still don't see it.

Drupal 6.15 and the 6.x-4.x-dev version of e-commerce (although I tried a couple other versions).

My apologies if this has been covered elsewhere, I did not find it.