The "Virtual Piano" sessions are designed to support those choristers who do not have any instrumental lessons or who would like to find out how keyboard instruments work.
If you have a keyboard or piano at home - great, then do use these instruments. If you don't, there are two options:
Piano on your computer
This website provides a good virtual piano on your computer for free:
Here, you can play the notes using the keys on your computer.
Piano on your tablet or phone
There are many different (free) piano apps for your tablet or phone. The advantage is that you can play the piano keys directly with your fingers. Have a look with your parents and download the app you like best.
Short piano piece in C Major
This website tells you all you need to know about accidentals in a nutshell: