After copying %%PREFIX%%/etc/pam_smb.conf.example to
%%PREFIX%%/etc/pam_smb.conf and editing it to taste,
add something like this to your /etc/pam.conf file to use
this module:

login    auth    sufficient    %%PREFIX%%/lib/pam_smb_auth.so

Then be sure and rename %%PREFIX%%/etc/rc.d/pam_smbd.sh.sample
so that the daemon starts at boot time.

See %%PREFIX%%/share/doc/pam_smb for more information.