routing

Hi,
I have a router CISCO 1721 in my US office.And a same kind of router in my indiam office too.I ahve few systems connected to to therouter in the INDIAN office.I just want to know how all my systema in India uses the Router in US in order to access the internet. is there any routing algorithm for that(To be very simple my systems in my Indian office shud use the private IPS to access the internet thru my router in US.It would be great if the explanations are pretty clear .Because I am just going to implement the same…..without any changes.I am not a networking expert.It would be great if the responce is instantaneous and if it si sent to my E-mail address….stellavincy@yahoo.com

Regards,
Stella Vincent