Open Google Chrome and download the MetaMask extension to install it on your browser: https://metamask.io/download/
This will create a new wallet and Secret Recovery Phrase. Create Password and write the Secret Backup Phrase on a peace of paper and store in a secure location.
Create an account and include your Email Address and Links in the Profile Settings: https://opensea.io/login
If you want to get a Verified account or collection in OpenSea, follow the steps below: https://support.opensea.io/