The Dutch Patients' Federation and MedMij have created a sample PGO. Here, you can practice with a sample PGO at your own convenience.
You can practice with a PGO by going to the VoorbeeldPGO website or by clicking on this link:

Practicing with a PGO

Would you like to practice logging in via an authenticator? You can do so through a mini course.
To take the course, you need an account. You can create this before you start the course.
The mini-course can be taken here:

Mini-course: Logging into a PHR

NB! 
You are creating an account at PGO.nl. This is not a PGO where you can retrieve your data, but an information website.
When you want to use a PGO, select a PGO and create an account for it.