I would advise you to learn the basis and advance  MICROSOFT  EXCEL  as it will a basic requirment for any student who would join MBA in FINANCE . In the first year of your MBA degree , you will be learning all the basis like financial accounting , marketing management , organisational behaviour , human resource mangement , business communication , business development etc:  You will get an overall knowledge about the basis in MBA degree and in your second year you will learn about a particular branch like for you it is finance . So it is ok for you even you are from science . But do learn basis and advanced MICROSOFT EXCEL  as it will be very important in MBA in finance . You can take some basic online courses like basics of accounting , communication in business which will give you an confidence to cover topics in a subject faster .