Media Library Quota Exceeded

Hello,
I have read various posts about people media library quota being full with an error message along the line “Sorry, you have used all of your storage quota for this website”.
The website is hosted on our own hosted servers and is running wp 3.5.1. Most posts point to log in to your website and navigate to ‘my sites’ – ‘network admin’ – ‘dashboard’. Unfortunately no such options exist on our site when logged in as an admin.
Could anybody let me know why this my be occurring and how to change this? (as an aside, we are well within the storage limits for our hosting provider).

The blog I need help with is https://www.carmele.co.uk.