After you have created a project and BackStreet Browser has started download, the project is automatically saved to the folder specified by you as the output folder in the project properties dialog.
If you need to transfer a saved project into another folder, you don't have to navigate through your hard drive folders manually. Select the necessary project in the BackStreet Browser projects list and use the button "Copy to..." in the application toolbar (main menu item File\Copy to...) A copy of all downloaded filed of the project will be transferred to the folder you will specify in the appeared dialog.
In BackStreet Browser you can work not only with separate projects but with workspaces. A workspace is a set of projects that are processed simultaneously. You can operate only one workspace at a time but have as many saved workspaces as you need and switch among them. To know more about workspaces click here.