When you setup your Ubercart site, it is your responsibility to configure the payment settings to your liking. More information on that can be found on the Payment Settings page in the Configuring Your Store section of the User's Guide. You need to enable the payment methods you would like to receive and make sure the settings are adjusted to your liking. If you plan on processing credit card payments through your website, you will also need to install a payment gateway module that interfaces with a credit card web service. The Ubercart project does not configure or pay for any of these services for you. It is up to you to sign up for a service, enable the appropriate module, and configure it for your account.
Payment modules have been under development for a while now, and the latest list of compatible web services may be viewed at this page:
Core and contributed modules make possible a variety of payment methods, including check, credit card, PO, and special services like PayPal.