Authorisation is the process of linking your ReaderStore account with your Sony Reader or other mobile device, such as your Tablet or Mobile to allow eBooks purchased through the ReaderStore to be transferred to those devices.
For each account, you can authorise up to 6 devices. If you want to add a 7th device, you'll need to de-authorise one of the previous 6 first.
These videos take you through the step-by-step process of authorisation and deauthorisation:
For software updates, apps or additional help, visit the Reader Store.