To unlock files:
  1. In the Project Explorer, select the file to lock. If you select a folder, project, or solution, any eligible child items will also be unlocked.
  2. Choose Source Control > Unlock or press Ctrl+R, N.
  3. The dialog will list the files that can be unlocked.
  4. In that dialog, you can deselect any files you don't want to unlock.
  5. Click Unlock.

Enabling the VCS > Options > Unlock Immediately option will bypass the dialog and immediately unlock files.