For those who are already having XenForo earlier version installed & just want to upgrade to current release (ex: v2.1.3 to v2.1.4) follow the instructions:
XenForo Upgrade package doesn't contain "data" + "internal_data" folder and ".htaccess" file in the parent directory.
So either you can remove those folders, file & then upload . . . or, if you haven't changed anything in ".htaccess" file, then simply download & upload the whole package, it won't affect any existing data.