Though the main intention of this system is for all researchers to build onto the same overall family tree, each researcher adding information does so within their own branch. When you are adding new records, they will automatically belong to your own part of the overall tree. When you search, the search will default to searching within your own part of the tree, but at any point you can change the search to look across all branches of the tree contributed by all researchers.
The "Branch" choice on the main search page:
The "Branch" choice on the search results page: