This answer is relevant if your website has been designed and built by BT. View FAQs for Web Hosting if you built your website. If you're not sure which website package you have, please read How to get support for your website.
If your website is still not appearing after a few days of going live, check this by typing your whole website address into Google search.
If your website is found but your website is not found for specific search terms, then you'll need to update your website content to make sure the search term appears in your website content and in the titles of your pages.
This alone may not make your website appear in the first few pages of Google search, as there are many other factors that help rank your website for a specific keyword.