When given a two-year end balances eg. 2015 and 2016 And the cashflow is to be accounted for 2016, will I have to add the balances of 2015 to 2016 or will I have to use 2016 balances only without 2015?
It depends on which balances you are looking at, but it is the difference that we are interested in.
Statements of cash flows are explained in detail in my free lectures. The lectures are a complete free course for Paper F3 and cover everything needed to be able to pass the exam well.