I know that in order to get the Windows side to work, I would have to manually enter the username and password from a terminal window (not the dial up networking box). To do this, just check "Bring up terminal windows after dialing" from the modem configuration box. You will then enter the username and password that you have set up to use the /usr/lib/ppp/ppp shell.
Looking at other notes that I have on the setup process:
Create a user that has /usr/lib/ppp/ppp as a shell. This user and its password is the one you will above.
Our entry in /etc/ppphosts looks like the following:
*fveppp idle=10 reqtmout=3 conf=10 term=2 nak=10 mru=296 noipaddr local=pppserver remote=pppclient
fveppp is our user name and pppserver and pppclient are entries in /etc/hosts where we put the IP addresses that we wish to assign them. I know there are ways to use /etc/ppppool to do the latter step, but that is not necessary for our application with SCOPPP.