As donald said for creating a responsive website you need to have knowledge of HTML and CSS. Assuming you may have knowledge of at least basic HTML and CSS, these tips can be helpful for creating a basic responsive html website.
1. While creating responsive website you define css for different screen size, new css will be override the original css which use for the desktop version.
2. Create a page and make it responsive so you can use it this page for other services page.
3. Read some article on google which will help you in detail.
4. at the starting create some simple design so you can make it easily.
5. download extension in Google chrome to check your design on mobile devices.