To access a source file that hasn't been mounted in
Filesystems, select Open File from the File
menu.
The Open dialog box appears, and you can browse for the file
you want to open. Once you've selected a file, the Select Mount
Point dialog lets you choose where to mount it.
After you press Mount, the file opens in the
Editor window and file's directory is mounted in Filesystems and displayed
under the Filesystems tab in the Explorer.