How should a Network Tech Protect a Small Buisness Network?

1st. The person responsible for information security
(CISCO)- Chief Information Security Officer
I know the security principles: layering, limiting, diversity, obscurity, and so on.
Using effective authentication methods
Audit Information Security Scheemes.

I know about all of the above, but need some advice on how to go about it.

Help is greatly appreciated, I'm reviewing my next courses chapters and got stuck on this end of chapter question. I want to be ahead of the game when the semester starts. Thank you again.