You can uninstall or removes an installed boxshade package itself from Ubuntu 16.10 (Yakkety Yak) through the terminal,
$ sudo apt-get remove boxshade
If you would like to remove boxshade and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove boxshade
If you use with purge options to boxshade package all the configuration and dependent packages will be removed.
$ sudo apt-get purge boxshade
If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.
$ sudo apt-get purge --auto-remove boxshade