In NV, we do not have a first-disclosure rule and no part of the Nevada Revised Statutes requires you to declare a firearm in the car unless asked.
However.....as a CCW holder, the gun will most likely be on my hip or in the holster attached to the dash. So what I do, as I hand over my DL with CCW in the same jacket, I say in a very polite and respectful voice "officer, I have a valid Nevada concealed carry permit and a handgun which is located (fill in the blank)", if I already have the leather jacket containing my DL and CCW permit. Another variation is to keep both hands on the steering wheel (don't put your hands outside the window, felons do that!) as I tell the officer that I have a permit first, then a handgun second, and third the location of the gun. Remember the order, and remember, a polite and respectful tone of voice!
If however the gun is elsewhere, and assuming I know why I am being pulled over (burned out headlight or such) and have no reason to believe the officer is going to want to search my car or ask me to exit my vehicle, I do not say anything until I am asked about "any guns, knives, grenades" in the car.
In NV, the CCW approval information is linked to your DL which is also linked to your vehicle registration, so they already know who the car is registered to and that the registered owner has a CCW even before they exit their vehicle during a traffic stop.
NV is an open carry state, but some local jurisdictions have restrictions, for instance in Clark County and North Las Vegas you cannot carry a loaded handgun anywhere in the car unless you have a CCW permit.
It is vital to know what the laws are in the jurisdictions you travel thru. What is true in one place may not be true in another place, and can place you in a bad spot.
This is information that one can get when attending a CCW class, which I strongly encourage all armed citizens to take, if only for the legal background information that is provided in such classes.
Cheers!