How do you charge the Ki gauge?

This must be done quickly......
"Tap", then hold down the Guard button.

In other words....quickly press (then release), then hold down the guard button.

When in battle just hold X and press left(or right depending on your position) 2 times and on the second time hold it

Just hold X and press left (or right depending on your position) 2 times and on the second time hold the button(<-- or -->)

Thanks for your help.

Quickly press square then double click the opposite side your opponent is

Hold square and triangle at same time -.-