I had same problem after my long road trip where I broke one of my fog lamps. I also did not know how to do it. But I looked for the manual from the other forum and used it. The process for me to change them was not easy. My first try was really hard and frustrating, but I have had to do it twice already and it was easy the second time.
Find the manual and the chapter that refers to changing the fog. It was not easy for me to easily locate that chapter. If you find it, it will be easier. Let me try to explain to you how to do it, based on how well I remember doing it myself. I just hope it will make sense to you. If it doesn't, please, just find the manual and it will help you. That is what helped me.
What I remember doing is you have to pry off those 2 chrome things in front of the fog. It has 4 hooks. You have to pry it out from the hooks. I think they are in the position of 12, 3, 6, 9 and 12 on the clock. So, pry them from those points. Be careful. You could break something. Try prying 2 sides (say the 9 position and 6 position) close to each other slowly. (I think it was easier starting from the area where the piece is largest on the side, which is on the outer sides, moving towards the inside). You cannot get one off completely without the next close one following at same pace. Then when you get it out, set it aside. Go under the truck now and feel behind the fog and find the one and only screw you have to take out. One of mine was rusted. I could not find any store that could have it except the dealership. I went and ordered 4. I needed only 2, but I bought 4. I think all 4 cost about $10 out the door. I got the screw off each fog and when I replaced it, I replaced with oem new screw. It made the job easier when re-installing it. So, I recommend you buy the screws before you start. You need only 2. I bought 4. And I just have the other 2 sitting somewhere as spare. When you take that screw off, feel exactly under the bulb itself in the middle, there is a plastic piece still holding it in place. This is hard to do. Pry it, while pushing the bulb out. Be careful or it will fall off and shatter. If you get that, the fog bulb would come off.
It is easy now to do it in reverse to install your new fogs. My picture below gives you an idea. I took many pictures while doing this process as I love to document things for my personal use. But I decided not to post the pictures of the steps when I was doing this. They are still on one of my other memory cards.
http://www.clubarmada.com/forums/18-infiniti-qx56/56441-major-maintenance-2012-infiniti-qx56-9.html