How to set the store PayPal account?
Default PayPal account can be selected on the Admin/Database tab.
Go to Admin/Settings menu, Database tab, you can find the Default Pay Pal Account dropdown and Use Live PayPal Server checkbox in Financials section.
You can select a PayPal account or create a new PayPal account
By checking "Use Live PayPal Server" checkbox, all purchases from the store will be real money transactions, uncheck this checkbox to use PayPal sendbox server (test server), no real money transfered.
To create a account, please select PayPal as account type, and you need to have your PayPal account's API username, password and signature
To obtaining your PayPal API signature credentials, please refer Creating and Managing Classic API Credentials
PS: please clone the template-store site and call it "store" for your online store