$ sudo apt-get update
$ sudo apt-get install juju-1.25 

juju-1.25 is installed in your system.

Make ensure the juju-1.25 package were installed using the commands given below,

$ sudo dpkg-query -l | grep juju-1.25 *

You will get with juju-1.25 package name, version, architecture and description in a table

juju-1.25 package basic information: