At Raylo, we only offer the option to add or remove insurance at the time of application. Because this is a part of your hire agreement, it cannot be changed retrospectively.
If you wish to add insurance after the purchase, you would have to go with a separate provider. Before you do, there are a couple of things we'd recommend to check:
does the insurance cover you outside of your home;
what's the excess; and
does it cover loss, theft and accidental damage.
For more details on using your own insurance, see here.