$ sudo apt-get update
$ sudo apt-get install elpa-expand-region 

elpa-expand-region is installed in your system.

Make ensure the elpa-expand-region package were installed using the commands given below,

$ sudo dpkg-query -l | grep elpa-expand-region *

You will get with elpa-expand-region package name, version, architecture and description in a table

elpa-expand-region package basic information: