To activate a 30 day trial licence, after you have created a screen, press the 'Activate' button and then press 'Active licence and show PIN'. This will apply a trial licence to your screen and allow you to see the screen's PIN. 

You will notice that now on your screen dashboard it will give you a timeframe until the license runs out. If you wish to extend this licence, you will have to purchase it on a monthly, yearly or 3 yearly basis.