Your domain name is the subject of your website. It doesn't make sense if you purchase cars.com to create a website about flowers. Think again.
If you already have a hosting plan and domain name and you want to install a script to create your website, you need to go into your control panel > File Manager and follow the installation instructions that came with the script. Your host should be able to help you more with this if you contact them.
People really should not buy domains, without having a plan or researching how to do wha they want. Also with such vage posts, your just wasting peoples time. With the domain? the script? tweeking? html? what. Read about hosting, read about websites and how they function and provide more details. Geez