You should select items that are the farthest from the root of the directory tree: the Add to Source Control command for any given file or directory also adds any parent directories (up to the VOB root directory) that are not already elements. For example, if neither \guivob\hello_world nor \guivob\hello_world\src are elements, you can add both directories to source control by adding \guivob\hello_world\src to source control.