To link your domain with Google email first of all you must have:
A Purchased domain name.
Website ready.
DNS record or auto connect instructions.
Once you have made sure that you have all three of them:
Login into your DNS console.
Add Web host record to your console.
Your domain will be redirected to your website immediately but the process could take up to 72 hours to complete.
But in case the process still clings on even after the completion of 72 hours, contact your domain host support immediately.