Do you have to use ViewNX 2 with Nikon?

This may be a silly question, but I just got a Nikon camera (the p500) and the software ViewNX 2 came with it for pictures. Do i have to download it to use or can I just continue using what I have already like Picassa?

You can use what ever you want. I have heard "Picasa" is a great program, if you are familiar with it there's no reason to add to your learning curve!