How can I get Siri to glow around my iPad screen?

I believe that the "glow" that you are talking about is a visual effect that you get along with Apple Intelligence.

Apple Intelligence - Apple

Which iPad do you have? To get Apple Intelligence, it has to be one of these:

If you have one of those models, see:

Get started with Apple Intelligence on iPad - Apple Support

If you do not, then you cannot have that feature on your iPad.

You can get it with Apple Intelligence but your iPad had to be support with Apple Intelligence Your iPad has to be a iPad Pro M1 and later a iPad Air M1 and later a iPad Mini A17 Pro if you have these iPad’s then you can have the glowing Siri effect with Apple Intelligence