Install and enable APCu on a Asustor AS7004


I am trying to speed up my Owncloud service by using a cache (APCu preferredly), but I cannot manage to get it installded and running. I have of course posted the same question in Asustors forum but not yet received any reply.

I simply dont know how to set it up on my server.

Were do I begin? I have downloaded the repo, but it disappears and is therefore not installable via SSH. I have also manually downloaded it to a location of my choice and then tried installing via its location, also without any success.

Some info about my setup.

Server configuration
Operating system: Linux/ADM
Web server: Apache 2.2.31
Database: MySQL
PHP version: 5.6.14
ownCloud version: 9.1.2

Any help is much appreciated.
Thank you in advance!