There is a ton of information in the Wiki here. Below is the link for that scanner. Scroll down to "Related Pages" for even more links to pages which will help educate you. Get a Premium Membership and it is easy to download from the RadioReference database and program to your scanner using FreeScan.
BCT15X - The RadioReference Wiki
The Easier to Read Manual linked in the post above mine is a great help too. Don't get overwhelmed most of it's features you will probably never even use. Just go slow and one system at a time.
Read up on Programming, Operating, and especially Quick Keys. In the Wiki read the first 4 links in
Trunking, as your fire agencies use this trunked system
Countywide Coordinated Communications System (CCCS).
CHP is conventional and is easier to program.
Orange County CA Frequencies is the link to your county page. Take note of the
mode columns. Anything P25 or (D) is digital and your scanner can not decode it. Also anything (E) encrypted can not be decoded on any scanner.
And there is always help here. I had a BCT15 and a BCT15X until my area started to go digital.