I would double check to make sure that you have power steering fluid in the pump.
Make sure it is a the correct level
If you have power steering fluid in the system and the level is correct then I would look at changing the pump

In short
To change the pump
You will have to remove the belt
You will need a puller to remove the pulley off the pump.
You can get to the bolts in the pump by the holes in the pulley.
The reason why you would need to remove the pulley is because the new pump does not come with it
Disconnect the power steering lines.
Should be a bolt on the back side of the pump as well

To install do the reverse order

After the pump is installed,
Jack the front wheels off the ground
Add fluid
Start the car and turn the wheels left to right a few times.
Do not hold the steering full left or full right
This will bleed the system

I do not believe in adding additives to a system. Most of the time, its someone or a company getting rich off of us the consumer.