internet remote access via host T1

Our corporate office users have access to the internet via a T1. We have 6 other remote offices who I want to give access to the Internet via our T1 at the corporate computer center. Can the other offices gain access to our T1 by going through their router to the corporate router to the T1? If not, how do I accomplish this? We are running Windows NT 4.0 and have a frame relay hook-up to our other offices.
Thank you for your time.