How to Create Products – free and non-free

I’m not very familiar with WordPress, but I can create Pages. After creating Checkout, Login and Members, I tried to create Products. Not my first time to do this, had a previous hosted account which became inaccessible because I messed up in connecting my domain name to my blog. But in there I successfully created products.

However in this new account, I always get this message: THE CHECKOUT HAS NOT BEEN CONFIGURED. I’m sure I have the right shortcode, it’s so easy. But can’t figure out what’s wrong. Please help, here’s my blog.