Jacks or jackstands should be placed under the frame.
Look under the car and you will see what appears to be a frame built into the floor pan. Place the jack stands under those frame rails.
You need to place the floor jack under the actual beam of the car frame. This is where 2 jacks may have to be put into play. You will need to jack up the car high enough to be able to release the old shocks from their bases. You may have to put a jack on blocks to jack the car high enough to achieve this. Put your stands on very stable blocks under the frame as well.
there is a place for the jack on the sub frame. it looks like a thin lip of metal that runs all the way down the sub frame. look for where it gets thicker and put your jack stand under it, but get it as close to the front of the car as you can.
Jack it up by placing a floor jack under the frame.
if its a 4 wheel drive vehicle just put jack under chunk on front axle. if 2 wheel drive then put jack on metal A shaped brace that goes from frame and shock to each wheel.
A floor jack is the safest way to jack it up. Place the jack under the frame.
Under the frame close to the wheel coming off.
under the right rear seat
You should put the jack on the frame like it says in the instruction manual, but its hard to do from there i would suggest that you should put it on the axel, it may or may not work, i have not tried it, but its really hard to push the jack up on the frame.
The safest spot to jack for normal tire changes is the cutouts just behind the front wheels and just in front of the rears. There are also frame jack-points a bit deeper under the car, four in the front but just the differential case itself in the rear. Either way, don't put anything you'd like to keep in it's current condition under the car when it's just supported by just a jack itself - use jack-stands.
Under the frame of the truck not the oil pan or exhaust.