Struggling to understand commercial awareness articles

Try reading the FT and the Economist.

Persistence is the key. It's a bit like learning a language, it's difficult at first when you keep having to google what terms mean and why a concept is important, but the understanding does build as your "fluency" increases.
The economist is good and well written - most articles in there shouldn't be too tricky to get your head around after a while. I personally don't think the FT is particularly helpful, it's way beyond what you need to know about the economy and financial markets as a vac schemer or a trainee (and frankly much beyond that too!), BBC business news pages are honestly probably all that you need. The Guardian too (no paywall), depends on your politics of course but I like their business coverage.
Other than that, have a google for some blogs or sites that cover wider commercial, technological, political and financial issues and how they affect law firms and the "business of law".
That should be more than enough to see you through a vac scheme and TC. Don't worry about it too much either - all these concepts get much clearer once you're in the workplace.

Thank you; this helped a lot.
In interviews how would we sort of apply this knowledge? Do we speak of the common themes and patterns that we see and how they relate to certain departments in the law firm?