[racket] "Which topic categories would you like to subscribe to?"...

How do I select "topic categories"?
Where do I define "topic categories"?

Under Racket list serve settings I see the following setting:

"Which topic categories would you like to subscribe to?" |No Topics Defined|

Clicking on the box containing the words "No Topics Defined", does nothing.

Do I need to first define topic categories?

Where can I view existing topic categories?

All of these questions above relate to my item (a) below.
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I like to receive emails from the Racket list serve that are in response to my
questions, not the questions of others, therefore, I believe I need to do one of
the following:

Filter emails that I receive from the Racket list serve by either:
(a) Filtering on the racket list serve, OR 
(b) Filter emails with my email reader (Gmail).

What is recommended?
Thanks