Rey,
If you want all 8 PSTN to go to PBX port 1, you do realize that if one call is active, then no other calls will go through.
To do this you should create a 2nd pbx trunk group, move channels 2 through 8 to the new trunk group then make sure that passthru is set to Yes on both pstn 1 and pbx 1.
If you need further help on configuration, you can contact me at mike_voip@hotmail.com
Mike