You can add existing files to a project in a number of ways.

To add existing files to the active project:

Using the Open File dialog, navigate to the directory containing the files and select the ones you wish to add to the project.

The selected files are added to the folders whose filter matches the extension of each of the files. If no filter matches a file's extension, the file is placed underneath the project node.

To add existing files to a specific project:
  1. In the Project Explorer, right-click the project to which you wish to add a new file.
  2. Choose Add Existing File.
To add existing files to a specific folder:
  1. In the Project Explorer, right-click the folder to which you wish to add a new file.
  2. Choose Add Existing File.

The files are added to the specified folder without using filter matching.