you need to qualify for at least one of the four hardships set forth in the IRS guidelines
this isn't a bank account, you can't just take money when you wish
If you are unemployeed and vested in the program you have the choice to roll over the money or cashout you will lose at least 30% of thye vested value depending on the plan
if you are working you should be able to take a loan of up to 80% of the vested value

That information should be available from the benefits office where you work. If you don't have a benefits office, ask your supervisor.