There are many ways for you to prepare for your viva. The Vitae website https://www.vitae.ac.uk/doing-research/doing-a-doctorate/completing-your-doctorate/your-viva/viva-checklist gives the following checklist of suggestions helpful in preparing to defend your thesis:

- I know my thesis thoroughly

- I have written a one-page summary of each chapter

- I have continued to work with my thesis after submission or have begun to prepare a conference paper or publication

- I am able to explain how my thesis fits into the big picture

- I have kept up to date with relevant literature

- I know what the implications of my research are to both theory and practice

- I have had a mock viva with my main supervisor

- I have asked my peers to quiz and challenge me about my thesis

- I have explained my thesis to friends and family who are not familiar with it

- I have investigated the backgrounds and publications of my examiners

- I have looked at my institution's guidelines for vivas

- I have produced a list of likely questions

- I have identified areas of my thesis that are likely to be challenged

- I have marked up my thesis to help me refer to it in the viva

- I know how I will be informed of the outcome of my viva.

For more advice, you could look at How to survive your viva by Rowena Murray (ISBN 0-335-21284-0) or The Doctoral Examination Process: A handbook for students, examiners and supervisors by Penny Tinkler and Carolyn Jackson (ISBN 978-0-335-21305-4).