Can I directly use a professor's suggestion?
Yes, you can. If the professor did not want you to use his words verbatim, he'd have described the ideas, but not provided words. Example:


  You could say about how you organized a public talk on this topic to convey your interest.


This gives you an idea of what to write about, but doesn't give you the exact thing to write.

Of course, you don't have to use his words if you think you can express the same idea better in your own words.