In WooCommerce 2.2, the Simplify Commerce gateway was added to WooCommerce. This is huge news, because Simplify Commerce is a really user-friendly gateway and it processes credit cards without taking you to another site (unlike PayPal). Simplify Commerce is pretty easy to set up and doesn't require a merchant account as some older processors do. If you're just getting started, Simplify Commerce is an excellent payment gateway to use.
An SSL certificate is required to process actual credit cards. Contact your host about setting one up on your site. You don't need an SSL certificate for testing.
There are some other technical hardware requirements listed at http://docs.woothemes.com/document/simplify-commerce/.
In order to configure the Simplify Commerce gateway, go through the following steps:
At this point, you can charge credit cards. It's advisable to do a few test orders. To do those, you'll need to enter your sandbox API credentials.
By default, the Description field will say something like Pay with your credit card via Simplify Commerce by Mastercard. I suggest simplifying this to Pay with your credit card. Most customers don't know or care what Simplify Commerce is. They just know that they want to pay with their credit card.