Lifting the Skyline is necessary for almost any maintenance procedure, and using a jack-lift to do so can be difficult to figure out. Honestly, it took me at least a few hours of mucking about trying to figure it out while making sure I was being safe the first time I did this. There's a big risk in doing something like this, you need to take every precaution necessary to stay safe, always have a buddy with you too.
Some people have managed to completely ruin their cars by improper lifting, trying to jack the car up using the frame rails or worse the floor panels will without doubt, result in a damaged chassis, just don't do it like that. This, is the proper way to do it, safely, with out damaging anything. Note: E-brake should be on.
Step 1, if your car is low - which it probably is - you're going to need to drive your front wheels up onto a set of blocks, just enough so you'll have enough space for the jack to slide under the front bumper.
At the rear, looking under the car locate the rear differential. Just in front of the rear diff, you will see a circular subframe support, the rear drive shaft actually passes right through the center of the hole. This is your rear jacking point, it is solid and will not cause any damage here.
Begin lifting the rear until you have enough height that you can slide 2 jack stands onto the rear subframe to support the weight, I use the triangular metal pieces where the subframe meets the chassis, there is a large bushing and bolt which holds the subframe to the chassis.
Slowly lower the jack allowing the car to come into position on all 4 jack stands now, and remove the jack lift from under the car. Putting the car back on the floor is the exact same but in reverse. Never work on your car with the vehicle weight supported only by jack lift, it's too dangerous and not worth the risk.