Selecting Specific Computers In Locations

I have already setup a network between Windows 7 x64 Ultimate machines. However, I am adding more computers to the network and would like to select as to which computers can see a particular folder. The problem is that when I am trying to set the permissions and go to "Locations," the only computer listed is mine, even though the "Network" folder clearly lists three other computers. How can I get these computers to also appear in "Locations" so I can choose which ones to share my files with? Ideally I am trying to create a new user group that will consist of preselected computers.