The 3 most important things which govern your complete 2 years of MBA are Powerpoint, Excel and Microsoft Word. You will need to write lots of reports, a do lot of work in excel and unlimited presentations. So, use online youtube videos and learn excel and powerpoint in detail, not the basic one which everyone knows. Also if possible do some online course to improve your writing skills.

You should also start reading lots of good novels written by good authors like Charles Dickens, Agatha Christie, Sydney Sheldon etc. This will help you in improving your English Literature. For improving your vocabulary you should start memorizing 3 words daily with their meaning and correct pronunciation. You should start using these words in your daily life so that you can memorize them in a better way and your communication skills also improve.

Also if possible do some communication skill crash course because in MBA during those 2 years or after passing out from the college in this real world, no matter in which department you go, good and effective communication is a must.

If you are interested in finance so you can give exam like CFA but this is the worldwide exam and are very tough you need to have prior knowledge of finance if you want to give this exam. Also you can do various stream online courses on sites like coursera, edx where courses are available free of cost.

But the most important thing is you should not do any of these things for a sake of your MBA exam preparations because this is the most important thing and without scoring very well in any of the exams you won't get admission in any of the good b-school and without good college all other preparetions will be wasted. It will not add much value in lifting your career.

All the best!!