Cant.. you have to put money into the account where you plan on trading stock, and paypal, stormpay, ect's fees are too great that they only accept CC's...
You have to put your money from PayPal/Stormpay into your bank account first, then wire the money back out to a brokerage account (or transfer everything via check, which takes longer). I'd recommend Scottrade or Firstrade for brokerage accounts, I've used both and they are great.