Withdraw use a localbitcoins.
HYIP are usually ponzi schemes.
To withdraw your coin into fiat currency you need to use an exchange. You set up a wallet on the exchange, link a bank account and then sell the Bitcoin for your local fiat currency and that exchange should send the funds to your bank account.
Alternatively you can get a bitcoin debit card, there are several. Some are prepaid debit cards and others will withdraw funds directly from your bitcoin wallet. The only stipulation with this option is that you're leaving your bitcoin (usually) in bitcoin until the moment you're ready to buy something with it. Not a bad option, just something to consider if you're trying to get out of Bitcoin but don't want to spend your funds.