How can I manage my time ?

Firstly you must allocate your time – it is 1.8 minutes per mark and so you should spend no more than 72 minutes on Section A, and in section B 18 minutes for 10 mark questions and 27 minutes for 15 mark questions.

You will not finish every part of every question, but that does not matter – it is better to have all questions part finished than only some questions fully finished and some not attempted. You are aiming for 50% on every question.

In Section A, again you are aiming for 50%. So you should look for the short / easy questions first, before you spend time on the longer ones. Any you either cannot answer or do not have time to answer then you must guess.

In Section B calculation parts, the marks are for the workings, not for the final answer. It doesn’t matter if you don’t finish – you are aiming for 50% then you have passed.
For the written parts, you must always write something. Even if it is something you do not know much about, anything sensible is likely to get a mark and just one mark is everything if you would otherwise fail on 49%.

One of the best ways to manage your time i believe begins before the exam by practicing as much past papers as possible. When you do that you develop a routine and minimize the time you take in the exam wondering where to begin.
and as John says use the clock stick to the time for each question.