I took the vanilla 737-800 airplane and made a flight plan : IFR from VOR to VOR. I am good until I need to set  start my approach and set my Nav 1 frequency. Where do I get the info ? I've look at some tutorial online but they were not using my plane so I am little confuse about the sequence and I need to perform for this plane.  I am trying to learn the correct procedure before I jump to the PMDG. Any help would be appreciated.

The absolutely simplest way is to popup the G500 GPS onscreen and use it to find the airport you are planning to land at. There will be a list of frequencies that you can scroll through and auto-tune your NAV1 Standby radio to the localizer (ILS) frequency.

 

Alternatively, you can bring up the Map view then hover the mouse cursor over the localizer/ILS feather and read the frequency from the popup tooltip.

 

The third method would be to search out the charts for your arrival airport and get the information from them. Be aware though that unless these are "flightsim charts" the frequencies list on "real world charts" may well be different.

In the Flight Planner, when you put in your origination airport, tell it the gate etc., THEN you put in your Destination airport, click button for ILS - then  you can check route - make sure "feathers" are turned on in this screen, AND zoom IN until you can see the green ils feathers - put your mouse over one of the feathers and it will give you - Course / ILS nav frequency.  You can do this during the flight if ATC tells you a different runway for landing.  - It's real simple - takes me about 30 seconds to get all the info I need.

The which I can accomplish in about six seconds by using the G500's built-in function, without having to break the immersion by pausing the flight while I have the "Map" opened...

 

The proper way of course is as you suggested by making it a required part of your pre-flight planning, but knowing that it is highly likely that your assigned runway is probably going to be different from your carefully laid plans.

 

Just as in war, no flight plan survives contact with the enemy, um, I mean ATC...

When I use the flight planner, I write down ALL the ILS info, and as you say, ATC almost never uses the one shown.....

 

There are many very good and free utilities out there.  I use this one frequently: www.airnav.com/airports/ - gives you everything you could possibly want and need.

 

Should be a required par of ILS planning.

I must be doing something wrong. The plane never lines up. I always end up 90 degree square from the runaway. I did everything you told me. I set the frequency and it was active. I was hearing the Morse code beeping. I had the director set to 341 (salt lake city 34L). I get the final instruction and the plane is out of whack. Not only, am I way to high ( I couldn't get lower based on the ATC instruction) but the plane was way off after the Straight in command.  My switch was set to Nav instead of GPS. I've look at many tutorial on youtube.  I begin to doubt my own intelligence to perform something that seems to easy.

 

Edit

Ok I figured it out. I am an idiot after all. Nothing like a good dose of humility. Thanks P3D.