It is not common practice to place a lone project under source control. Typically, you place the entire solution that contains one or multiple projects, but the integration allows you this flexibility if you choose to perform this task. If you have not placed the solution under source control and you choose the Place Project command, an informational dialog box opens warning you that the solution has not yet been placed. If you desire to place only the project, then click Yes to continue.
This opens the StarTeam Association for xxx.sln dialog box, where xxx.sln is the solution name.