If you already have a website with your domain that is hosted outside Office 365 Small Business, it doesn’t move to Office 365 when you add your domain. You can keep hosting your website where it is, while you use Office 365 to host your email as well as use team sites, instant messaging, and so on.
In the domains setup wizard, select No, I have an existing website or prefer to manage my own DNS records. Then the wizard will guide you to set up your domain with your domain's DNS records hosted at your current DNS host. We recommend that you continue to manage your domain's DNS at your current DNS host to help prevent problems with access to your current website when you set up your domain with Office 365. If you don't have a website, you can opt to have Office 365 set up and manage DNS for your domain instead.
To get started using your domain with Office 365, you'll follow the steps in the domains setup wizard in Office 365. The setup wizard guides you through adding your domain to your Office 365 subscription, changing your email address (which is also your user ID for Office 365) to use your domain name, and setting up your users’ email addresses with your domain.