How do I identify a Nominalization so I can replace it with an Action Verb?

I’m taking a course on Plain Language and they state that Nominalizations are bad as they make a sentence longer. (There are a whole 12 people taking the course).

The course states that Nominalizations are nouns with Verbs hidden with-in them; but I’ve been unable to identify the nouns within the sentences as they all seem to me to be verbs.

I understand nouns to be person, places or things…but I keep identifying these Nominalizations as verbs…but I still don’t think I’m doing it right since when I find an example, I identify the wrong words as the Nominalizations and they don’t match up with the examples.

My goal is to shorten sentences by replacing the Norminalizations with Action Verbs…but I don’t know how to identify Norminaliazations to begin with.