1) Start by tightening all the four corner screws so that the springs are completely compressed.

2) Adjust the Z endstop screw such that the nozzle is about 1mm above the bed.

The endstop screws are actually M3 (3mm) screws with a thread pitch that is exactly 0.5mm.  This means that one complete turn of the screw will mean the bed-nozzle distance will change eactly 0.5mm.  If you turn the screw clockwise so that the screw becomes shorter, the nozzle to bed distance will become closer at the rate of 0.5mm for every complete clockwise turn.  if you turn the screw counter-clockwise such that the screw gets longer, the nozzle to bed distance will become farther at the rate of 0.5mm for every complete clockwise turn.

When adjusting the nozzle to bed distance, if you are trying to make the nozzle to bed distance farther away from each other, you can do so by turning the z adjustment screw  counterclockwise (to make the screw longer) with the assurance that there will be no disaster of the nozzle crashing on to the bed.

However, if you are trying to make the nozzle to bed distance closer to each other, you risk the accident of the nozzle crashing on to the bed.  So always turn the z adjustment screw clockwise (to make the screw shorter) a little at a time, and testing the adjustment by homing the z nozzle at every minute change.  Don't be too aggressive and impatient when turning the z screw clockwise (closer nozzle-bed distance).  Always do it a little at a time.  You may need to home the Z axis (nozzle) several times since you will probably need to adjust the z axis endstop adjustment screw several times.  Remember... do this only very slightly at every try to avoid nozzle crashing on the bed.

That all said.  and with the leveling system corner screws tightened up and springs fully compressed, adjust the z adjustment screw accordingly so that the nozzle is approximately 1mm above the bed.

3) With the nozzle-bed distance roughly adjusted to 1mm, you can then now proceed to "level" the bed.  You can do this while the machine is turned off (it's actually better to do it with the machine turned off because the x and y axis cannot be manually moved when the power is on).

a) Manually move the Y axis so that the bed is all the way back (Y axis home position).  
b) Manually move the X axis so that the nozzle is all the way to the left (X axis home position)

Then place a small piece of paper between the nozzle and the bed.  Turn the front left corner screw of the leveling bed counterclockwise so that the left-front corner of the bed will go up close to the nozzle... close enough for the piece of paper to slightly get caught when you pulll the piece of paper, but far enough so that the piece of paper can still be pulled out without
it tearing apart.

c) Manually move the x axis so that the nozzle is all the way to the right.

Then place a small piece of paper between the nozzle and the bed.  Turn the front right corner screw of the leveling bed counterclockwise so that the right-front corner of the bed will go up close to the nozzle... close enough for the piece of paper to slightly get caught when you pulll the piece of paper, but far enough so that the piece of paper can still be pulled out without
it tearing apart.

d) and e) Repeat the procedure  for the back-left and back-right corners.

You can check the height of the 4 corners again (if you are up to it).

That done, you now have a leveled bed, and the springs of the corner screws of the leveling system are still pretty much compressed such that the screws will not easily get loose during normal printing.