In all honesty this question is tricky as it can’t be learnt overnight. I’d have an understanding of M&A, what drives businesses, what are the issues they are facing in today’s market (not even too high level but think Brexit and trade tensions), and pick three news topics you can know inside and out.
By way of practice do some case studies and pick a business like the airline BA. Walk yourself through all the logistics of that business and think about the regulations they must comply with. Walk yourself through the customer experience to help you with this so from booking flights to maybe downloading the app and checking in online to buying some duty free perfume on the plane etc. These tips and starting points should hopefully help you