Territory / Group query

I am going to be adding two new users to Zoho, but I only want them to be able to have access to contacts and companies who are tagged to their territory (Circle). I do not want them to be able to see everything else we have on Zoho. So if users from the UK territory assign Circle as a territory, will these two Circle users automatically be able to see this? Not sure if I need to create a group or if this is something to do with territory management? Any help would be appreciated! Thanks.