You can use the open, append and merge commands to get files from the vault. Files are downloaded to the local working folder which is defined by the vault (for example, C:\Users\<USER>\My Documents\Vault in Windows 7).
The commands are located on the Vault tab, Access panel:
. Closes the file currently opened in Autodesk Navisworks and opens the file selected in the vault. You have a choice of opening the file as read-only, or checking it out for editing. You must check out the file to make modifications to it. The file is temporarily stored on your local drive while you make the changes. If the file stored in your working folder is older than the version in the vault, you are prompted to replace the working copy. If the working copy is currently checked out, it is not replaced.
. Adds the selected files to the currently opened scene.
. Merges the selected files into the currently opened scene. Any duplicate geometry and markup is automatically removed.