Click on database, click the browse button. A map will come up and then click on Arizona. To the right of the Arizona map on top, click on Arizona Federal. Scroll about half way down the page and you will find the Forest Service. Scroll down to the Tonto National Forest. I suggest you program the admin net and both fire nets. Scroll down to Common Use and program all three Forest Service Region 3 (AZ & NM) tactical frequencies. Next scroll down and program both Air Ambulance frequencies. These are used for air to ground comms if a firefighter has to be medevaced.
Then scroll down through the zone dispatch centers to Zone 6 - Phoenix Dispatch Center. Also, program 168.625, National Air Guard. This is an emergency channel for all fires. Ground crews can call aircraft with emergencies. Aircraft must have radios tuned into this frequencies at all times. If an aircraft can't be reached on any other frequency they can be called on this one. Same goes for the aircraft, if they can't reach dispatch or "air attack" they can use this frequency. They then arrange to communicate on another frequency. I'm almost certain they have a base station on Mt. Ord, which booms into Payson. This frequency is often just called "the guard."
Next, program in 168.650. This is "national" flight following. Pilots and dispatch will usually refer to it as just "national." Aircraft use this frequency to call dispatch when they arrive in the airspace of the various dispatch centers listed on the AZ Federal Page. They will then receive information on what frequency to switch to and contact the "Air Attack" who supervises and controls all air traffic over a fire. It would be done on one of the AM frequencies listed for each dispatch center, or an air to air AM frequency assigned specifically for a single incident (fires and other emergencies). If an aircraft is flying recon over a dispatch area they might stick to using "national" for flight flying or, more likely, they will switch to one of the Forest, Admin or Fire Nets.
Finally, click the back arrow until you get the national map of the database. Underneath the map is a highlighted text of "Nationwide Frequencies." Click on it and then scroll down to the Federal category. Scroll down to "National Interagency Fire Center" (NIFC). I suggest you set up a bank in your scanner you call "Federal Large Fire," which will contain all of the frequencies on this page. The UHF frequencies are used as links to and between repeaters and/or remote bases, which is what the aircraft links are used for. A fire does not always use these frequencies. I won't discuss all the ins and outs of how frequencies are assigned to incidents as that would take a while. Sometimes they use the frequencies listed for the NIFC system and sometimes they use frequencies assigned to other federal agencies in the area that are not currently used. A separate scanner that is set up to search the federal VHF band (162-173.9875) is needed to figure them out. Also a search of the AM band from 118-136 is needed to find the air to air frequencies in use. Those are actually assigned by the FAA after being contacted by NIFC.
Listening to daily traffic on local nets will be where the initial attack of a fire will occur. If the fire gets big enough to have a national Incident Management Team assigned is when the NIFC system will be employed. Sometimes frequencies will be announced over the air, especially on National Flight Following. That doesn't happen all that often as frequency changes are done the first shift after a management team takes the fire over and is done at the beginning of the next day shift and listed in the Incident Action Plan (IAP) (shift plan) that is printed and given to all resource supervisors (engine captains, crew superintendents, division supervisors, etc.). If frequency changes occur days or weeks later, they make them effective as of the start of a day shift and inform everyone via the IAP.
Most large fires result in having a thread started here in the Arizona forum. Sometimes other people have sources where they find out what frequencies are being used, or they have done a search and figured out some frequency uses. Make sure you click on those threads. If you find something share it!
If you have questions about the above or questions later, just ask.