New Z50 focus question

[Dtuck]

I have fast purchase a Z50. I have change my back button to focus.
Every time I push the back button to focus a bunch of green squares show up?.
I have watched several videos and all they have is a red square, they are able to put that square on what they want to focus on?
How do I accomplish this?
Thanks

 

[RAZKY]

I have fast purchase a Z50. I have change my back button to focus.
Every time I push the back button to focus a bunch of green squares show up?.
I have watched several videos and all they have is a red square, they are able to put that square on what they want to focus on?
How do I accomplish this?
Thanks

The answer should be in your User's Manual, but it seems that most any Nikon AF video ought to explain it. I don't use autofocus myself, so that's about the only advice I can offer.