It's possible that what you want to listen to might be on a trunked radio system.
Select your county of interest and go to the database page for the county. In the upper right are a series of links topped by "xxx County Trunked Systems." Click that link and it will take you to a list of trunked radio systems; check those for information on your local area (if any).
Just a quick glance shows me that Douglas County Public Safety is using a trunked system which cannot be "trunk-tracked", only monitored by scanning all the frequencies.
Best advice is to listen to the conventional frequencies first (for example, Klamath Sheriff on 155.535 MHz, etc). If you don't hear anything, then it's very likely they've moved to a trunked system.
If you're a complete newbie, I'd suggest reading the following tutorials:
wiki.radioreference.com
wiki.radioreference.com