folder security permissions

Hi,

I know it may sound a easy process for most of you but need help to make sure I am following correct method

I need to add a new security  group  for a folder that has lots of subfolders,  and folder that I am trying to change permissions of it is in a middle of a long folder directory.
 I need allow only  limited users to have access to it and also remove other groups that has inheritable permissions.

folder is in our SAN so I will be browsing the folder from one of our 2003 server

Can you please provide me step by step guide for this?

I can create the new group and add users into it in AD but my issue how to remove other groups from this folder and new one in and then remove others. I have to make sure that permission to folder is inherited its subfolders.