My small buisness:) Help

I am getting ready to start my small online buisness, but need a bit of help.... do I add paypal to my blog or do I just add a shopping cart? I just need to know if the information that I have is right, so that my buisness will run smoothly. If anyone has any information, would you please email me:) I need to get started ASAP because I have some Halloween items:)