Before you start to create your store, you need to make sure your customers' details are secure. You do that by obtaining an SSL certificate for your site.
To set up SSL in WordPress, you'll need to carry out two steps:
Most hosting providers or domain registrars will sell you an SSL certificate, which is normally the simplest way to go about it as they will complete the configuration with your domain name. Some hosting providers don't offer SSL certificates (notably, the cheaper ones), so it's worth checking when you're shopping around for hosting. Alternatively, ...