Lot of strange ideas as to what HSA flex accounts are.
These accounts are actually pretty useful. They have to be paired with a High Deductible Health Insurance plan. The idea is your health care comes out of your pocket for the first $2500 or so (this varies). If it goes above that, you're 100% covered. The money before your deductible comes out of your Health Savings Account.
Health Savings accounts are kind of set up like free checking accounts at your bank. You have the freedom to use any bank you wish for your account (although your employer usually sets up a bank by default, you can change it any time). You put money in your savings account- usually pre-taxes- and it's usually deducted directly from your paycheck. If you have it deducted post-taxes, you have to organize your spending receipts and you get deductions when you file your taxes, which is a pain. Pre-tax is much better.
The account itself usually gives your a Mastercard of Visa debit card. When you have a medial expense, you can either charge it to your card, or write a check. If you don't have enough to pay for a bill, most doctors allow you to make payments out of the HSA account (say, $50 per pay).
These accounts are actually pretty nice if you're healthy. The money stays in the account, and if you accumulate over $2000, many banks will put the money in a market fund that gains high interest. You can even withdraw remaining funds when you retire tax free.
If you have medical problems or use expensive prescriptions, you may want to consider traditional insurance with prescription coverage. Otherwise you'll be forking out a lot of up-front cash every year.