Once you have been sent your invitation to graduation, you will be offered the chance to purchase 2 guest tickets for your ceremony. At a later date, depending on the size of the ceremony, there may be an opportunity to purchase extra guest tickets, though this is never guaranteed.
For the meantime, please have a look around the Congregations pages on the Kent website (linked below) which should provide you with some more information about your day.
https://www.kent.ac.uk/congregations/index.html
As you will see, there are sections for what to do and expect before, during and after your graduation, as well as a frequently asked questions (FAQs) section. There is also information about gown hire with the Graduate Gowning Company and photography from H Tempest Ltd on the day.