After you have successfully purchased your training you will be automatically redirected to the training area. Just click on the "My Training" tab in the navigator to start your training.
You should be able to see your purchased training and/or assessments in the training list. Click on the title link to start your training.
Alternatively, after purchase you will be sent an email that contains your user name and password. Use these details to log into your training area by clicking on the Login tab in the navigation bar.