Postgis installation

I am installing Postgis on my Debian server, following these instructions:

http://ift.tt/1JTtDJt (Ubuntu / Debian)

http://ift.tt/1e2XYnN

However, after following the instructions it looks like I have installed PostGres (9.4), but no PostGIS.

Do I have to install something more that was omitted in the instructions?

Can I somehow add PostGIS as a PostGres Plugin?