The main entry point to begin using the GCD Software is the Project Menu:

In the GCD Software, all change detection analyses that you do are performed within a specific project. A project consists of three primary elements:

1. A folder (fixed path) on your file system where the project and its contents exist.
2. A *.gcd Project File
3. All the GCD input and output files (in Inputs and Analyses subfolders of project folder)
   

From the Project Menu, you can create New... projects, Open... existing projects and Close the current project. You can always tell if a project is open because it will be listed by its name in the GCD Project Explorer:

In addition to the above commands, the GCD Project Explorer can be accessed from the Project Menu, the Project Properties can be reviewed and the description edited, and you can Browse GCD Project Folder.