If you have Workstation installed with the appropriate Subscription License, you should proceed to your customer area to download the updates. If you don’t know your customer ID and password, you contact our sales team and they will help you. Your customer area holds all your license information and allows you to open support enquiries.
If, on the other hand, you are using an evaluation version, you can download the evaluation of the latest release and install that. I suggest you read the following documentation about updating the software,
https://www.nomachine.com/AR10K00698 and https://www.nomachine.com/DT03O00129#2.1.