kleopatra software package provides certificate Manager, you can install in your Ubuntu 16.04 LTS (Xenial Xerus) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install kleopatra
kleopatra is installed in your system.
Make ensure the kleopatra package were installed using the commands given below,
$ sudo dpkg-query -l | grep kleopatra *
You will get with kleopatra package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | Network |
| Package | kleopatra |
| Version | 4:15.12.3-0ubuntu1 |
| Description | certificate Manager |
| Sub Section | Net |