To connect a domain to your website, go to the Dashboard and then Domains.
Click on Connect An Existing Domain to open the field to enter a domain and click Next.
After adding the domain a screen with 2 DNS records will show. These are the records you need to add to your domain settings in your domain provider. Every domain provider should allow you to add these records to your domain, if you can't find them you can contact your domain provider and ask how to add them. They will connect your domain to your website.