A FEW DEFINITIONS

AO : Animation overrides, are scripts which control your avatar with animations and poses. For example : walk, run, jump, swim, fly, sit, stand and sit on the ground.

HUD AO: is an AO which appears as an additionnal menu on your SL screen. This menu allows you to switch between different actions of your AO, like walk, sit, ground, stand etc...

How do I use it?

Simply wear it. The hud will appear in the right of your screen with buttons.
If you want to change the walk, just click on the walk button and access to the walk menu.
It's the same for sit , ground sit and load.
Make sure the ao is on .

If you need to dance somewhere or simply want your AO to be off click on ' AO ON' and it'll switch to off.
It's just as simple as that.