Activating a Theme

The theme you link to is on wordpress.COM

Your website uses wordpress.ORG

http://en.support.wordpress.com/com-vs-org/
Shows the difference

You can’t activate a .com theme to a .org site. You need to find a theme to download and install!

http://wordpress.org/support/topic/post-formats-in-manifest-theme?replies=15
This thread contains a link to the .svn repo for the .COM manifest theme – you could try to download it and install it to your site – I’m not 100% it would work… but I would think it should

https://codex.wordpress.org/Using_Subversion

It’s not really something I can explain easily (I just fumbled through using it, I am no expert by a long shot)…. you would need an svn client – I was able to figure out tortoisesvn pretty handily

You basically install it, point it to the server URL, and it works kind of like windows explorer, you check out the theme using it and that gets you the files

http://wordpress.org/support/topic/use-wordpresscom-theme?replies=33
has a pretty lengthy discussion that may help too