Firstly, locate the power steering fluid container under your bonnet. It will usually be marked in writing or with a picture of steering wheel.
Visually inspect the Minimum and Maximum level markings to gauge how much power steering fluid is present. Unscrew the cap and top up the liquid accordingly.
If the levels are low it could mean that you have a leak in the power steering system. If the levels get below the minimum level markings it could lead to a failure in your power steering which is very dangerous.
Checking your power steering fluid should be part of your monthly motor checks.